Heterocyclic compounds

ABSTRACT

The present invention relates to a heterocyclic compound of the following general formula (I):                    
     wherein X is sulfur atom, oxygen atom or —NR 3 — (R 3  may form a heterocyclic ring or a substituted heterocyclic ring with R 1  via the nitrogen atom), 
     R 1  is alkyl group, substituted alkyl group, aryl group, substituted aryl group, heterocyclic group or substituted heterocyclic group, and 
     R 2  is hydrogen atom, halogen atom etc.; 
     or its pharmaceutically acceptable salt and interferon inducers, antiviral agents, anticancer agents and therapeutic agents for immunologic diseases comprising the compound (I) or its pharmaceutically acceptable salt as active ingredients.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP98/05318 which has an Internationalfiling date of Nov. 26, 1998, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to novel heterocyclic compounds havinginducing activity for biosynthesis of interferon. The heterocycliccompounds of the present invention induce biosynthesis of endogenousinterferon in a living body, and are useful for medicines, such asantiviral agents, anticancer agents and therapeutic agents forimmunologic diseases.

BACKGROUND OF THE ART

It has been recently determined that endogenous interferon plays notonly central role to bio-defensive mechanism against virus infectionsand microbial infections, but also an important role dn antitumor andimmune modulator. Mass production of interferon is established. Namely,it is possible to obtain of natural interferon by cell culture and alsoto produce a large amount of recombinant interferon from E. colitransferred with a gene of interferon and therefore, many researchachievements on these interferons have accumulated. For example, manykinds of biological activity on interferon, such as antiviral activity,prevention of cell growth and immune modulation have been confirmed andinterferon is practiced on clinics as treating agents for virus infecteddiseases, such as hepatitis C and hepatitis B, anticancer agents andtherapeutic agents for immunologic disease. Furthermore, it is suggestedthat interferon will prevent carcinogenesis by hepatitis C and hepatitisB.

Since there is no therapeutic method for almost of the above diseases,interferon is especially made much of.

DISCLOSURE OF INVENTION

The object of the present invention is to provide novel low molecularweight compounds having inducing activity for biosynthesis ofinterferon, and interferon inducers, antiviral agents, anticancer agentsand therapeutic agents for immunologic diseases comprising thesecompounds as active ingredients.

Viruses of many kinds of animals, microbes such as mycobacteria andprotozoa, extracts of them, mitogen, specific antigens andimmunopotenciators are known as inducers for biosynthesis of interferon.It is known that for example, many kinds of natural double strand RNAS,synthesized double strand RNAs such as poly-I:C, and anionic highmolecular compounds such as polyacrylic acid and oxyamylose oxidizedwith chlorite have inductive activity of interferon.

On the other hand, among low molecular weight compounds have been foundfluorenones, pyrimidine derivatives, anthraquinones, acridines and so onhaving inductive activity of interferon (Stringfollow, D. A.: Methods inEnzymology, 1981, 78, 262).

However, when these compounds are used in clinical trial, their inducingactivity of interferon is unexpectedly low and these compounds have sideeffects or by administering them repeatedly, their inducing activity ofinterferon decreases and therefore, development on these compounds hasnot succeeded. Furthermore, imidazo-quinolines are known as interferoninducers among low molecular compounds. However, it is known that thesecompounds are inferior in selective interferon inducing activity andsimultaneously induce cytokines such as IL-6, TNF-α, etc (Testerman, T.L., et al.: J. Leukocyte Biol., 1995, 58, 365).

As the result of extensive investigation of interferon biosynthesisinducers among low molecules, the present inventors have found that theheterocyclic compounds of the present invention have excellentinterferon biosynthesis inducing activity.

The present invention relates to a heterocyclic compound of thefollowing general formula (I):

wherein X is sulfur atom, oxygen atom, —NR³— (in which R³ is hydrogenatom, alkyl group or substituted alkyl, or may form a heterocyclic ringor a substituted heterocyclic ring together with R¹ via the nitrogenatom),

R¹ is alkyl group, substituted alkyl group, aryl group, substituted arylgroup, heterocyclic group or substituted heterocyclic group, and

R² is hydrogen atom, or one or more substituents on the benzene ring,and said substituent is the same or different and is hydroxy group,lower alkyl group, substituted lower alkyl group, lower alkoxy group,substituted lower alkoxy group, lower alkanoyl group, substituted loweralkanoyl group, aroyl group, substituted aroyl group, carboxyl group,lower alkoxycarbonyl group, substituted lower alkoxycarbonyl group,amino group, lower alkylamino group, di(lower alkyl)amino group,carbamoyl group, lower alkylcarbamoyl group, di(lower alkyl)carbamoylgroup, halogen atom, nitro group or cyano group; or a pharmaceuticallyacceptable salt thereof.

Further, the present invention relates to a pharmaceutical compositioncomprising a heterocyclic compound of the above formula (I) or itspharmaceutically acceptable salt as an active ingredient.

Further, the present invention relates to an interferon inducer, anantiviral agent, an anticancer agent and a therapeutic agent forimmunologic diseases comprising a heterocyclic compound of the aboveformula (I) or its pharmaceutically acceptable salt as an activeingredient.

Furthermore, the present invention relates to a process for preparing aheterocyclic compound of the above formula (I) or its pharmaceuticallyacceptable salt.

Groups R¹, R² and R³ in the formula (I) are explained below.

In R¹ alkyl group includes straight or branched C₁₋₁₀ alkyl group (e.g.methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl,1-methylpropyl, 3-methylbutyl or hexyl), C₃₋₇ cycloalkyl group (e.g.cyclopropyl, cyclopentyl, cyclohexyl or cycloheptyl), andalkyl-substituted C₃₋₇ cycloalkyl group, preferably straight or branchedC₁₋₆ alkyl group (e.g. methyl, ethyl, propyl, butyl or pentyl), and C₅₋₇cycloalkyl group (e.g. cyclopentyl or cyclohexyl).

In R¹ substituted alkyl group means the above alkyl substituted by thesame or different and one or more substituents.

Said substituents include cycloalkyl group (C₃₋₆ cycloalkyl group, suchas cyclopropyl, cyclopentyl or cyclohexyl), hydroxy group, lower alkoxygroup (C₁₋₆ alkoxy such as methoxy, ethoxy, propoxy, butoxy or pentoxy),substituted lower alkoxy group (substituted C₁₋₆ alkoxy group, such asmethoxyethoxy, ethoxyethoxy, hydroxyethoxy or chloroethoxy), aminogroup, alkylamino group, cyano group, nitro group, acyl group, carboxylgroup, lower alkoxycarbonyl group (C₂₋₇ alkoxycarbonyl group, such asmethoxycarbonyl or ethoxycarbonyl), halogen atom, such as fluorine atom,chlorine atom or bromine atom, mercapt group, lower alkylthio group(C₁₋₆ alkylthio group, such as methylthio, ethylthio, propylthio orbutylthio), substituted lower alkylthio group (substituted C₁₋₆alkylthio group, such as methoxyethylthio, methylthioethylthio,hydroxyethylthio or chloroethylthio), aryl group (C₆₋₁₀ monocyclic orfused cyclic aryl group, such as phenyl or naphthyl), substituted arylgroup (substituted C₆₋₁₀ monocyclic or fused cyclic aryl group, such as4-hydroxyphenyl, 4-methoxyphenyl, 4-fluorophenyl, 4-chlorophenyl or3,4-dichlorophenyl), and heterocyclic group (5-6 membered saturatedheterocyclic group containing nitrogen atoms from 0-2 and oxygen atomsfrom 0-2, such as piperidyl, piperazinyl, morpholinyl,tetrahydrofuranyl, pyrrolidinyl, pyrazolinyl or 1,3-dioxolanyl, 5-6membered unsaturated heterocyclic group, such as furyl, pyrrolyl,pyrazolyl, imidazolyl, thiazolyl, thienyl, pyridyl or pyrimidinyl, orbicyclic unsaturated heterocyclic group, such as indolyl, isoindolyl,quinolyl, benzothiazolyl, chromanyl, benzofuranyl or phthalimino).

In R¹ aryl group means C₆₋₁₀ monocyclic or fused cyclic aryl group, suchas phenyl or naphthyl.

In R¹ substituted aryl group means the above aryl group substituted bythe same or different and one or more substituents.

Said substituent includes lower alkyl group (C₁₋₆ alkyl group, such asmethyl, ethyl, propyl, butyl, cyclopentyl or cyclohexyl), hydroxy loweralkyl group (hydroxy C₁₋₆ alkyl group, such as hydroxymethyl,2-hydroxyethyl or 3-hydroxypropyl), lower alkoxy lower alkyl group (C₁₋₆alkoxy C₁₋₆ alkyl group, such as 2-methoxyethyl, 2-ethoxyethyl or3-methoxypropyl), hydroxy group, lower alkoxy group (C₁₋₆ alkoxy group,such as methoxy, ethoxy, propoxy, butoxy or pentoxy), cyano group, aminogroup, substituted amino group, lower alkoxycarbonyl group (C₂₋₇alkoxycarbonyl group, such as methoxycarbonyl, ethoxycarbonyl orpropoxycarbonyl), acyl group, nitro group, halogen atom, such asfluorine atom, chlorine atom or bromine atom, aryl group (C₆₋₁₀monocyclic or fused cyclic aryl group, such as phenyl or naphthyl),substituted aryl group (substituted C₆₋₁₀ monocyclic or fused cyclicaryl group, such as 4-hydroxyphenyl, 4-methoxyphenyl, 4-chlorophenyl or3,4-dichlorophenyl), and heterocyclic group (alicyclic or aromaticheterocyclic group containing nitrogen atoms from 1-2 and oxygen atomfrom 0-1, such as pyrrolidinyl, piperidyl, piperazinyl or morpholinyl).

In R¹ heterocyclic group means monocyclic saturated heterocyclic group,or unsaturated monocyclic or fused heterocyclic group containing atleast one heteroatom, that is, 0-3 nitrogen atoms, 0-1 oxygen atom and0-1 sulfur atom.

Said saturated monocyclic heterocyclic group includes 5 or 6 memberedsaturated heterocyclic group, such as tetrahydrofuranyl, pyrrolidinyl,morpholinyl, piperidyl, piperazinyl or pyrazolidinyl. Said unsaturatedmonocyclic heterocyclic group means 5 or 6 membered unsaturatedheterocyclic group, such as furyl, pyrrolyl, pyrazolyl, imidazolyl,thiazolyl, thienyl, pyridyl or pyrimidinyl. Said unsaturated fusedheterocyclic group means unsaturated bicyclic heterocyclic group, suchas indolyl, isoindolyl, quinolyl, benzothizolyl, chromanyl orbenzofuranyl.

In R¹ substituted heterocyclic group means the above heterocyclic groupsubstituted by the same or different and one or more substituents.

Said substituents include lower alkyl group (C₁₋₆ alkyl group, such asmethyl, ethyl, propyl, butyl, cyclopentyl or cyclohexyl), hydroxy loweralkyl group (hydroxy C₁₋₆ alkyl group, such as hydroxymethyl,2-hydroxyethyl or 3-hydroxypropyl), lower alkoxy lower alkyl group (C₁₋₆alkoxy C₁₋₆ alkyl group, such as 2-methoxyethyl, 2-ethoxyethyl or3-methoxypropyl), hydroxy group, lower alkoxy group (C₁₋₆ alkoxy groupsuch as methoxy, ethoxy, propoxy, butoxy or pentoxy), cyano group, nitrogroup, halogen atom, such as fluorine atom, chlorine atom or bromineatom, amino group, substituted amino group, lower alkoxycarbonyl group(C₂₋₇ alkoxycarbonyl group, such as methoxycarbonyl, ethoxycarbonyl orpropoxycarbonyl), acyl group, aryl group (C₆₋₁₀ monocyclic or fusedcyclic aryl group, such as phenyl or naphthyl), substituted aryl group(substituted C₆₋₁₀ monocyclic or fused cyclic aryl group, such as4-hydroxyphenyl, 4-methoxyphenyl, 4-chlorophenyl or 3,4-dichlorophenyl),and heterocyclic group (alicyclic or aromatic heterocyclic groupcontaining nitrogen atoms from 1-2 and oxygen atom from 0-1, such aspyrrolidinyl, piperidyl, piperazinyl or morpholinyl).

In R² lower alkyl group includes C₁₋₆ alkyl group (e.g. methyl, ethyl,propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl,1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl,1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl).

In R² substituted lower alkyl group means the above alkyl substituted bythe same or different and one or more substituents.

Said substituents include hydroxy group, lower alkoxy group (forexample, C₁₋₆ alkoxy group, such as methoxy, ethoxy or propoxy),carboxyl group, lower alkoxycarbonyl group (for example, C₂₋₇alkoxycarbonyl group, such as methoxycarbonyl, ethoxycarbonyl orpropoxycarbonyl) and halogen atom, such as fluorine atom, chlorine atomor bromine atom.

In R² lower alkoxy group means C₁₋₆ alkoxy group, such as methoxy,ethoxy or propoxy.

In R² substituted lower alkoxy group means the above alkoxy groupsubstituted by the same or different and one or more substituents.

Said substituents include hydroxy group, lower alkoxy group (C₁₋₆ alkoxygroup, such as methoxy, ethoxy or propoxy), carboxyl group, loweralkoxycarbonyl group (C₂₋₇ alkoxy-carbonyl group, such asmethoxycarbonyl, ethoxycarbonyl group or propoxycarbonyl) and halogenatom, such as fluorine atom, chlorine atom or bromine atom.

In R² lower alkanoyl group means C₁₋₆ alkanoyl group, such as formyl,acetyl, propanoyl, butanoyl, pentanoyl or hexanoyl.

In R² substituted lower alkanoyl group means the above alkanoyl groupsubstituted by the same or different and one or more substituents.

Said substituents include hydroxy group, lower alkoxy group (C₁₋₆ alkoxygroup, such as methoxy, ethoxy or propoxy), carboxyl group, loweralkoxycarbonyl group (C₂₋₇ alkoxycarbonyl group, such as methoxycarbonylor propoxycarbonyl) and halogen atom, such as fluorine atom, chlorineatom or bromine atom.

In R² aroyl group means C₇₋₁₁ aroyl group, such as benzoyl or naphthoyl.

In R² substituted aroyl group means the above aroyl group substituted bythe same or different and one or more substituents.

Said substituents include hydroxy group, lower alkoxy group (C₁₋₆ alkoxygroup, such as methoxy, ethoxy or propoxy), carboxyl group, loweralkoxycarbonyl group (C₂₋₇ alkoxycarbonyl group, such asmethoxycarbonyl, ethoxycarbonyl or propoxycarbonyl) and halogen atom,such as fluorine atom, chlorine atom or bromine atom.

In R² lower alkoxycarbonyl group means C₂₋₇ alkoxycarbonyl group, suchas methoxycarbonyl, ethoxycarbonyl or propoxycarbonyl.

In R² substituted lower alkoxycarbonyl group means the abovealkoxycarbonyl group substituted by the same or different and one ormore substituents.

Said substituents include hydroxy group, lower alkoxy group (C₁₋₆ alkoxygroup, such as methoxy, ethoxy or propoxy), carboxyl group, loweralkoxycarbonyl group (C₂₋₇ alkoxycarbonyl group, such asmethoxycarbonyl, ethoxycarbonyl or propoxycarbonyl) and halogen atom,such as fluorine atom, chlorine atom or bromine atom.

In R² lower alkylamino group means amino group substituted by C₁₋₆ alkylgroup (e.g. methylamino, ethylamino, propylamino, butylamino).

In R² di(lower alkyl)amino group means amino group substituted by thesame or different and C₁₋₆ alkyl group (e.g. dimethylamino,diethylamino, ethylmethylamino).

In R² lower alkylcarbamoyl group means carbamoyl group substituted byC₁₋₆ alkyl group (e.g. methylcarbamoyl, ethylcarbamoyl, propylcarbamoyl,butylcarbamoyl).

In R² di(lower alkyl)carbamoyl group means carbamoyl group substitutedby the same or different and C₁₋₆ alkyl group (e.g. dimethylcarbamoyl,diethylcarbamoyl, ethylmethylcarbamoyl).

In R² halogen atom means halogen atom such as fluorine atom, chlorineatom, bromine atom or iodine atom.

In R³ alkyl group includes straight or branched C₁₋₁₀ alkyl group (e.g.methyl, ethyl, propyl, butyl, pentyl, hexyl) and C₃₋₇ cycloalkyl group(e.g. cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl), preferablystraight or branched C₁₋₆ alkyl group (e.g. methyl, ethyl, propyl,butyl, pentyl), and C₅₋₇ cycloalkyl group (e.g. cyclopentyl,cyclohexyl).

In R³ substituted alkyl group means the above alkyl group substituted bythe same or different and one or more substituents.

Said substituents include cycloalkyl group (C₃₋₆ cycloalkyl group, suchas cyclopropyl, cyclopentyl or cyclohexyl), hydroxy group, lower alkoxygroup (C₁₋₆ alkoxy, such as methoxy, ethoxy, propoxy, butoxy orpentoxy), amino group, cyano group, aryl group such as phenyl,substituted aryl group, such as 4-hydroxyphenyl, 4-methoxyphenyl,4-chlorophenyl or 3,4-dichlorophenyl, nitro group and halogen atom, suchas fluorine atom, chlorine atom or bromine atom.

Heterocyclic ring formed together with R³ and R¹ via the nitrogen atommeans 5 or 6 membered saturated heterocyclic ring, such as1-pyrrolidinyl, 4-morpholinyl, 1-piperidyl, 1-piperazinyl or1-pyrazolidinyl, and 5 or 6 membered unsaturated heterocyclic ring suchas 1-imidazolyl.

Substituted heterocyclic ring formed together with R³ and R¹ via thenitrogen atom means the above heterocyclic ring formed together with R³and R¹ via the nitrogen atom alkyl substituted by the same or differentand one or more substituents.

Said substituents include lower alkyl group (C₁₋₆ alkyl group, such asmethyl, ethyl, propyl, butyl, cyclopentyl or cyclohexyl), hydroxy loweralkyl group (hydroxy C₁₋₆ alkyl, such as hydroxymethyl, 2-hydroxyethylor 3-hydroxypropyl), lower alkoxy lower alkyl group (C₁₋₆ alkoxy C₁₋₆alkyl, such as 2-methoxyethyl, 2-ethoxyethyl or 3-methoxypropyl),hydroxy group, lower alkoxy group (C₁₋₆ alkoxy, such as methoxy, ethoxy,propoxy, butoxy or pentoxy) and cyano group.

The compound (I) of the present invention forms an equilibrium mixturewith a tautomer represented by the following formula (Ia):

The compound (I) of the present invention may forms a salt with an acid.

The preferable acids are pharmaceutically acceptable acids, includinginorganic acids, such as hydrochloric acid, sulfuric acid, hydrobromicacid, etc., organic acids, such as acetic acid, oxalic acid, citricacid, malic acid, tartaric acid, fumaric acid, maleic acid, etc.

Further, in case of the compound (I) having an acidic substituent, thecompound may form a salt with a base.

The preferable bases are pharmaceutically acceptable bases, includinginorganic bases like alkali metals, such as sodium or potassium, ororganic bases, such as triethylamine or pyridine.

Preferable embodiments among the compounds (I) of the present inventionare as follows.

(a) A heterocyclic compound of the formula (II):

wherein X¹ is sulfur atom, oxygen atom or —NR^(3a)— in which R^(3a) ishydrogen, C₁₋₆ alkyl group, or substituted C₁₋₆ alkyl group, or may forma heterocyclic ring or a substituted heterocyclic ring together withR^(1a) via the nitrogen atom,

R^(1a) is C₁₋₆ alkyl group, substituted C₁₋₆ alkyl group, aryl group,substituted aryl group, heterocyclic group or substituted heterocyclicgroup, and

R^(2a) is hydrogen atom, or one or more substituents on the benzenering, and said substituent is the same or different and is halogen atom,C₁₋₆ alkoxy group, nitro group or hydroxy group; or

its pharmaceutically acceptable salt.

(b) A heterocyclic compound of the above (a) wherein X¹ is sulfur atom.

(c) A heterocyclic compound of the above (a) wherein X¹ is oxygen atom.

(d) A heterocyclic compound of the above (a) wherein X¹ is —NH—.

(e) A heterocyclic compound of the above (a) wherein X¹ is —NR^(3a)— inwhich R^(3a) means C₁₋₆ alkyl group or substituted C₁₋₆ alkyl group.

(f) A heterocyclic compound of the above (a) wherein R^(3a) forms aheterocyclic ring or a substituted heterocyclic ring together withR^(1a) via the nitrogen atom.

(g) A heterocyclic compound of any of the above (a)-(d) wherein R^(1a)means C₁₋₆ alkyl group or substituted C₁₋₆ alkyl group.

(h) A heterocyclic compound of any of the above (a)-(d) wherein R^(1a)means C₁₋₆ alkyl group substituted by C₁₋₆ alkoxy, hydroxy, halogenatom, cyano, trifluoromethyl, pyridyl, phenyl, tolyl or thienyl.

(i) A heterocyclic compound of any of the above (a)-(d) wherein R^(1a)means C₁₋₆ alkyl group.

(j) A heterocyclic compound of any of the above (a)-(d) wherein R^(1a)means C₃₋₆ cycloalkyl group.

(k) A pharmaceutically acceptable salt of a heterocyclic compound of anyof the above (b)-(j).

The compound (I) of the present invention has excellent inducingactivity for biosynthesis of interferon and shows in general thefollowing structure activity-relationship between R¹ and R² of thecompound (I).

The inducing activity for biosynthesis of the compound (I) of thepresent invention is influenced by length or size of R¹. For instance,the activity at the minimum concentration reaches best when carbonnumber on the group of R¹ is around 3 or 4 and therefore, it showsbell-type activity-relationship.

On the other hand, although the activity at the minimum concentrationwhen carbon number on the group of R¹ is around 1 or 2 is inferior tothe activity when carbon number on the group of R¹ is around 3 or 4, theformer is superior to the latter in induction amount of interferonjudging from the view of the production of interferon.

Therefore, when R¹ is alkyl group, preferable range of carbon number inthe view of the activity is 1 to 8, more preferably 3 to 5.

Preferable embodiments of alkyl group in R¹ are methyl, ethyl, propyl,butyl, pentyl, isopropyl, isobutyl, 1-methylpropyl, 3-methylbutyl,cyclopentyl and cyclohexyl.

Furthermore, it has been made clear that in case that R¹ is substitutedalkyl group, the activity is also influenced by size or length of R¹.

That is, the activity is influenced by total size or length of R¹including a substituent (e.g. lower alkoxy, hydroxy, halogen atom). Forinstance, preferable range of length in the view of the activity is 1 to8, more preferably 3 to 5 by calculating in carbon number as the same asin alkyl group in R¹.

Preferable embodiment of alkyl group in R¹ are 2-hydroxyethyl,3-hydroxypropyl, 4-hydroxybutyl, 2-aminoethyl, 3-aminopropyl,4-aminobutyl, methoxymethyl, 2-methoxyethyl, 3-methoxypropyl,ethoxymethyl, 2-ethoxyethyl, methylthiomethyl, 2-methylthioethyl,3-methylthiopropyl, 2-fluoroethyl, 3-fluoropropyl, 2,2,2-trifluoroethyl,cyanomethyl, 2-cyanoethyl, 3-cyanopropyl, methoxycarbonylmethyl,2-methoxycarbonylethyl, 3-methoxycarbonylpropyl, benzyl, phenethyl,4-pyridylmethyl, cyclohexylmethyl, 2-thienylmethyl,4-methoxyphenylmethyl, 4-hydroxyphenylmethyl, 4-fluorophenylmethyl, and4-chlorophenylmethyl.

When R¹ is aryl group or substituted aryl group, the same tendency asabove is observed. The most preferable embodiment of aryl group orsubstituted aryl group in R¹ are phenyl, 4-methoxyphenyl,4-hydroxyphenyl, 4-fluorophenyl and 4-chlorophenyl.

When R¹ is heterocyclic group or substituted heterocyclic group, or R³forms heterocyclic ring or substituted heterocyclic ring with R¹, thesame tendency as above is also observed. The most preferable embodimentsof heterocyclic group or substituted heterocyclic group in R¹ are1-pyrrolidinyl, 4-morpholinyl and 3-(2-hydroxyethyl)-1-pyrrolidinyl.

Preferable X are sulfur atom, oxygen atom and nitrogen atom which may besubstituted, in order.

Although influence by R² on inducing activity for biosynthesis ofinterferon is not so remarkable as that by R¹, preferable embodiments ofR² are hydrogen atom, halogen atom such as fluorine atom or chlorineatom, hydroxy group, lower alkoxy group such as methoxy, and nitrogroup.

A preferable substituent of R² and its position among the aboveembodiments is 4-fluoro, 4-chloro, 4-hydroxy, 4-methoxy, 4-nitro,2,4-difluoro, 2,4-dichloro, 3,4-difluoro, 3,4-dichloro, or3,4-dimethoxy.

Process for preparation of the compound of the present invention.

The compound of the present invention can be prepared by the followingmethods. However, starting materials which are not described below areprepared in accordance with the following methods, known methods, or inaccordance with known methods.

PROCESS 1

wherein R¹, X and R² are the same as definition in the formula (I), Y isleaving group such as halogen atom (e.g. chlorine atom, bromine atom),R⁵ is alkyl group, and R^(a) and R^(b) are hydrogen atom, or mean aminoprotective group because they are protected by an amino protective groupon the way of reaction, if necessary.

Compound (3) is prepared by reacting compound (2) with NHR^(a)R^(b) inan aqueous solution or in an organic solvent.

NHR^(a)R^(b) can be used about equal molar or large excess amount tocompound (2).

Organic solvents are alcohols, such as methanol, ethanol, propanol orbutanol, ethers such as tetrahydrofuran, 1,4-dioxane or diglyme, oraprotic solvents, such as dimethylformamide, dimethyl sulfoxide,acetonitrile or hexamethylphosphoroustriamide [(CH₃)₂N)₃P].

The reaction temperature is selected from the range between roomtemperature and about 200° C.

Reaction vessels such as an autoclave etc. may be used in the reaction,if necessary.

Compound (5) is prepared by reacting compound (3) and compound (4) inthe presence of a base in an organic solvent.

Compound (4) can be used about equal molar or several molars to compound(3).

Bases are inorganic bases such as alkali metal carbonates (e.g. sodiumcarbonate, potassium carbonate), or organic bases, such as tertiaryamines (e.g. triethylamine, diisopropylethylamine) or pyridines (e.g.4-dimethylaminopyridine, pyridine). The base is preferably used aboutequimolar to compound (4)

The organic solvents are halogenated hydrocarbons such astetrachloromethane, chloroform or methylene chloride, ethers such asdiethyl ether, tetrahydrofuran or 1,4-dioxane, or aprotic solvents, suchas dimethylformamide, dimethyl sulfoxide, acetonitrile orhexamethylphosphoroustriamide.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

Compound (6) is prepared by reacting compound (5) with Br₂ in an organicsolvent.

A reaction promoter such as sodium acetate may be added to the reactionmixture.

Br₂ is used from equimolar to several moles of compound (5), preferablyfrom equimolar to one and one-half moles.

The organic solvents are halogenated hydrocarbons, such astetrachloromethane, chloroform or methylene chloride, ethers, such asdiethyl ether, acetic acid, or carbon disulfide.

The reaction temperature is selected from the range between about 0° C.and around boiling point of the solvent.

Compound (7) is prepared by reacting compound (6) and an alcohol such asmethanol in the presence of a base in an organic solvent.

The base are alkali metals, such as sodium or potassium, alkali metalhydrides, such as sodium hydride or potassium hydride, organometalliccompounds, such as methyl lithium, butyl lithium or lithiumdiisopropylamide.

The base is preferably used from about equal molar to about two times asmuch to compound (6).

The organic solvents are ethers, such as diethyl ether, tetrahydrofuranor 1,4-dioxane, or aprotic solvents, such as dimethylformamide, dimethylsulfoxide, acetonitrile or hexamethylphosphoroustriamide. The alcohol asthe reagent, such as methanol, ethanol, propanol or butanol may serve asa solvent.

The reaction temperature is selected from the range between about roomtemperature and around boiling point of the solvent.

Compound (8) is prepared by reacting compound (7) with R¹XH in anorganic solvent.

R¹XH is used from about equal molar to several molars to compound (7).

When X is oxygen atom or sulfur atom, the reaction is preferably carriedout in the presence of a base.

The bases are alkali metals, such as sodium or potassium, alkali metalhydrides, such as sodium hydride or potassium hydride, organometaliccompounds, such as methyl lithium, butyl lithium or lithiumdiisopropylamide. The base is preferably used about equimolar to R¹XH.

The organic solvents are aprotic solvents, such as dimethylformamide,acetonitrile or hexamethylphosphoroustriamide, or ethers such as diethylether, tetrahydrofuran or 1,4-dioxane or diglyme.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

Compound (9) is prepared by treating compound (8) with an acid in wateror a mixture of water and an organic solvent.

The acids are inorganic acids, such as hydrochloric acid or hydrobromicacid, or organic acids such as trifluoroacetic acid.

The organic solvents are ethers, such as diethyl ether ortetrahydrofuran, aprotic solvents such as dimethylformamide, alcohols,such as methanol, ethanol or propanol, or acetic acid.

The reaction temperature is selected from the range between about roomtemperature and around boiling point of the solvent.

PROCESS 2

wherein R¹, X and R² are the same as definition in the formula (I), Z ishalogen atom such as chlorine atom or bromine atom, or leaving groupsuch as methanesulfonyloxy or p-toluenesulfonyloxy, and Y and R⁵ are thesame as defined above.

Compound (11) is prepared by a method known by the skilled person. Forinstance, when Z is a chlorine atom, compound (11) is prepared byreacting compound (10) with phosphorousoxychloride.

The reaction temperature is selected from the range between roomtemperature and reflux temperature of the reaction solvent. When Z ismethanesulfonyloxy, compound (11) is prepared by reacting compound (10)with methanesulfonyl chloride in the presence of a base in an organicsolvent, and if necessary, NH₂ group on compound (10) is protected andthen deprotected.

The bases are inorganic bases such as alkali metal carbonates (e.g.potassium carbonate), or organic bases, such as triethylamine,diisopropylethylamine, 4-dimethylaminopyridine or pyridine.

The organic solvents are halogenated hydrocarbons such as methylenechloride, ethers, such as diethyl ether or tetrahydrofuran, or aproticsolvents such as dimethylformamide, etc.

The reaction temperature is selected from the range between about 0° C.and around boiling point of the solvent.

Compound (12) is prepared by reacting compound (11) with R¹XH in anorganic solvent.

When X is oxygen atom or sulfur atom, the reaction is preferably carriedout in the presence of a base. The bases are alkali metals, such assodium or potassium, alkali metal hydrides, such as sodium hydride orpotassium hydride, or organometalic compounds, such as methyl lithium,butyl lithium or lithium diisopropylamide.

The organic solvents are aprotic solvents, such as dimethylformamide,acetonitrile or hexamethylphosphoroustriamide, or ethers, such asdiethyl ether, tetrahydrofuran 1,4-dioxane or diglyme.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

Compound (13) is prepared by reacting compound (12) and compound (4) inthe presence of a base in an organic solvent.

The bases are inorganic bases such as alkali metal carbonates (e.g.sodium carbonate, potassium carbonate), or organic bases, such astertiary amines (e.g. triethylamine, diisopropylethylamine) or pyridines(e.g. dimethylaminopyridine, pyridine).

The organic solvents are halogenated hydrocarbons such as methylenechloride etc., ethers, such as diethyl ether or tetrahydrofuran, oraprotic solvents, such as dimethylformamide, dimethyl sulfoxide oracetonitrile.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

Compound (14) is prepared by nitrating compound (13) in an organicsolvent, for example by adding nitric acid thereto in an organic solventsuch as acetic acid.

The reaction temperature is selected from the range between about −20°C. and around the boiling point of the solvent.

Compound (15) is prepared by reducing nitro group on compound (14) in anorganic solvent.

The reducing agents are hydrogen, sodium borohydride or lithium aluminumhydride.

The organic solvents are alcohols, such as methanol or ethanol, esterssuch as ethyl acetate, etc., or ethers, such as diethyl ether ortetrahydrofuran.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

Compound (16) is prepared by reacting compound (15) with formic acid ortrimethyl orthoformate in the presence of an acid.

The acids are inorganic acids such as hydrochloric acid, or organicacids, such as p-toluenesulfonic acid or camphor sulfonic acid.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

Compound (17) is prepared by reacting compound (16) and Br₂ in anorganic solvent.

A reaction promoter such as sodium acetate may be added in thisreaction.

The organic solvents are halogenated hydrocarbons, such astetrachloromethane, methylene chloride or dichloroethane, ethers such asdiethyl ether, acetic acid, or carbon disulfide.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

Compound (18) is prepared by reacting compound (17) and R⁵OH in thepresence of a base in an organic solvent.

The bases are alkali metals, such as sodium or potassium, alkali metalhydrides, such as sodium hydride or potassium hydride, or organometaliccompounds, such as methyl lithium, butyl lithium or lithiumdiisopropylamide.

The organic solvents are ethers, such as diethyl ether ortetrahydrofuran, or aprotic solvents, such as dimethylformamide oracetonitrile. The alcohol used as the reagent, such as methanol,ethanol, propanol or butanol may be served as a solvent.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

Compound (19) is prepared by treating compound (18) with an acid inwater or a mixture of water and an organic solvent.

The acids are inorganic acids, such as hydrochloric acid or hydrobromicacid, or organic acids such as trifluoroacetic acid, etc.

The organic solvents are ethers, such as diethyl ether ortetrahydrofuran, aprotic solvents, such as dimethylformamide oracetonitrile, alcohols, such as methanol, ethanol or propanol, or aceticacid.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

PROCESS 3

wherein R¹, X and R² are the same as definition in the formula (I), andY is the same as defined above.

Compound (22) is prepared by reacting compound (20) and compound (21) inan organic solvent. The reaction can be carried out in the presence orabsence of a solvent.

The bases are inorganic bases such as alkali metal carbonates (e.g.potassium carbonate), or organic bases, such as tertiary amines (e.g.triethylamine, diisopropylethylamine) or pyridines (e.g.4-dimethylaminopyridine, pyridine).

The organic solvents are halogenated hydrocarbons such as methylenechloride, ethers, such as diethyl ether, tetrahydrofuran or 1,4-dioxane,or aprotic solvents, such as dimethylformamide, dimethyl sulfoxide oracetonitrile.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

Compound (23) is prepared by cyclizing compound (22) in water, anorganic solvent, or a mixture thereof. The reaction can be carried outin the presence or absence of a base.

The bases are inorganic bases, such as alkali metal hydroxide (e.g.sodium hydroxide, potassium hydroxide), alkali metal alkoxide (e.g.sodium methoxide) or alkali metal carbonates (e.g. potassium carbonate),or organic bases, such as tertiary amines (e.g. triethylamine ordiisopropylethylamine) or pyridines (e.g. 4-dimethylaminopyridine,pyridine).

The organic solvents are halogenated hydrocarbons such as methylenechloride, ethers, such as diethyl ether, tetrahydrofuran or 1,4-dioxane,aprotic solvents, such as dimethylformamide or acetonitrile, oralcohols, such as methanol, ethanol or 2-propanol.

The reaction temperature is selected from the range between roomtemperature and around the boiling point of the solvent.

Compound (24) is prepared by dehydrating compound (23) in an organicsolvent.

The dehydration agents are diphosphorus pentaoxide, dicyclohexylcarbodiimide, etc.

The organic solvents are halogenated hydrocarbons such as methylenechloride, or aprotic solvents, such as dimethylformamide oracetonitrile.

The reaction temperature is selected from the range between about roomtemperature and around the boiling point of the solvent.

When X is NH, compound (25) is prepared by reacting compound (24) andguanidine in the presence or absence of a base in an organic solvent orwithout any solvent.

The bases are inorganic bases, such as metal alkoxide (e.g. sodiummethoxide), alkali metal hydroxide (e.g. sodium hydroxide), or alkalimetal carbonates (e.g. potassium carbonate), or organic bases, such astertiary amines (e.g. triethylamine, diisopropylethylamine) or pyridines(e.g. 4-dimethylaminopyridine, pyridine).

The organic solvents are for example, alcohols, such as ethanol orbutanol, ethers, such as tetrahydrofuran or 1,4-dioxane, toluene, oraprotic solvents, such as dimethylformamide or dimethyl sulfoxide.

When X is oxygen atom, compound (25) is prepared by reacting compound(24) and urea in the presence or absence of a base in an organic solventor without any solvent.

The bases are inorganic bases, such as metal alkoxide (e.g. sodiummethoxide), alkali metal hydroxide (e.g. sodium hydroxide), or alkalimetal carbonates (e.g. potassium carbonate), or organic bases such astertiary amines (e.g. triethylamine) or pyridines (e.g.dimethylaminopyridine, pyridine).

The organic solvents are for example, alcohols, such as ethanol orbutanol, ethers such as tetrahydrofuran or 1,4-dioxane, toluene, oraprotic solvents, such as dimethylformamide or dimethyl sulfoxide.

Compound (25) is also prepared by reacting compound (24) and benzoylisocyanate in the presence or absence of a base in an organic solvent,and then by cyclizing the reactant in the presence of a base in water,an organic solvent, or a mixture thereof.

The bases used in the reaction with the isocyanate are alkali metalcarbonates such as, potassium carbonate, or organic bases, such astertiary amines (e.g. triethylamine, diisopropylethylamine) or pyridines(e.g. 4-dimethylaminopyridine, pyridine).

The organic solvents are for example, halogenated hydrocarbons such asmethylene chloride, ethers, such as diethyl ether or tetrahydrofuran, oraprotic solvents, such as dimethylformamide or dimethyl sulfoxide.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

The organic solvents used in the above cyclizing reaction are forexample, alcohols, such as ethanol or 2-propanol, ethers such astetrahydrofuran, or aprotic solvents, such as dimethylformamide ordimethyl sulfoxide.

The bases are for example, inorganic bases, such as alkali metalalkoxides (e.g. sodium methoxide), alkali metal hydroxide (e.g. sodiumhydroxide) or ammonia, or organic bases, such as tertiary amines (e.g.triethylamine) or pyridines (e.g. 4-dimethylaminopyridine, pyridine).

The reaction temperature is selected from the range between around roomtemperature and around the boiling point of the solvent.

When X is sulfur atom, compound (25) is prepared by reacting compound(24) and thiourea in the presence or absence of a base in an organicsolvent or without any solvent.

The bases are metal alkoxides (e.g. sodium methoxide), alkali metalhydroxides such as sodium hydroxide, alkali metal carbonates such aspotassium carbonate, tertiary amines such as triethylamine, or pyridinessuch as 4-dimethylaminopyridine or pyridine.

The organic solvents are alcohols, such as ethanol or butanol, ethers,such as tetrahydrofuran or 1,4-dioxane, toluene, or aprotic solvents,such as dimethylformamide or dimethyl sulfoxide.

Compound (25) is also prepared by reacting compound (24) and benzoylisothiocyanate in the presence or absence of a base in an organicsolvent, and then by cyclizing the reactant in the presence of a base inwater, an organic solvent, or a mixture thereof.

The bases used in the reaction with the isothiocyanate are alkali metalcarbonates such potassium carbonate, tertiary amines, such astriethylamine or diisopropylethylamine, or pyridines, such as4-dimethylaminopyridine or pyridine.

The organic solvents are halogenated hydrocarbons such as methylenechloride, ethers, such as diethyl ether or tetrahydrofuran, or aproticsolvents, such as dimethylformamide or dimethyl sulfoxide.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

The organic solvents used in the above cyclizing reaction are forexample, alcohols such as ethanol or 2-propanol, ethers such astetrahydrofuran, or aprotic solvents, such as dimethylformamide ordimethyl sulfoxide.

The bases are inorganic bases such as metal alkoxides (e.g. sodiummethoxide), alkali metal hydroxide (e.g. sodium hydroxide) or ammonia,or organic bases such as tertiary amines (e.g. triethylamine) orpyridines (e.g. 4-dimethylaminopyridine or pyridine).

The reaction temperature is selected from the range between around theroom temperature and around boiling point of the solvent.

Compound (26) is prepared by reacting compound (25) with R¹Y (wherein Ymeans leaving group such as halogen atom e.g. chlorine atom, bromineatom) in the presence of a base in an organic solvent. In this reactionNH₂ or OH group on compound (25) may be protected or deprotected, ifnecessary.

The bases are for example, alkali metal hydrogen carbonates such assodium hydrogen carbonate, alkali metal carbonates such as sodiumcarbonate, tertiary amines such as triethylamine, or pyridines such asdimethylaminopyridine or pyridine.

The organic solvents are for example, halogenated hydrocarbon such asmethylene chloride, ethers, such as diethyl ether or tetrahydrofuran, oraprotic solvents such as dimethylformamide.

The reaction temperature is selected from the range between about 0° C.and around the boiling point of the solvent.

When X is NH, compound (26) can be also prepared by reacting compound(24) and compound (27) in the presence or absence of a base in anorganic solvent or without any solvent.

The bases are metal alkoxides such as sodium methoxide, alkali metalhydroxides, such as sodium hydroxide, alkali metal carbonates, such assodium carbonate, tertiary amines such as triethylamine, or pyridines,such as 4-dimethylaminopyridine or pyridine.

The organic solvents are for example, alcohols, such as ethanol orbutanol, ethers, such as tetrahydrofuran or dioxane, toluene, or aproticsolvents, such as dimethylformamide or dimethyl sulfoxide.

The compound (I) of the present invention and an intermediate forpreparing it can be purified by the conventional method for example,column chromatography, recrystallization, etc.

The solvents for the recrystallization are for example, alcohols, suchas methanol, ethanol or 2-propanol, ethers such as diethyl ether, esterssuch as ethyl acetate, aromatic hydrocarbon, such as benzene or toluene,ketones such as acetone, hydrocarbons such as hexane, or aproticsolvents, such as dimethylformamide or acetonitrile, or a mixturethereof.

Furthermore, on carrying the above reaction, the protection ordeprotection techniques can be employed, if necessary. The protection ordeprotection techniques are described in detail in “Protecting group inOrganic Synthesis, by T. W. Greene and P. G. M. Wuts (1990)”.

When the compound (I) of the present invention has an asymmetric carbonatom, optical isomers exist and therefore, a mixture thereof and anisolated optical isomer are included in the compound (I) of the presentinvention.

The compound (I) of the present invention can be orally or parenterallyadministered as an interferon inducer. A compound such that wasmetabolized in vivo into the compound (I) of the present invention, orits equivalent compound, so-called “pro-drug” should be included in thecompound of the present invention.

The compound (I) of the present invention is generally administered inthe form of a preparation together with a pharmaceutical carrier. Saidpharmaceutical carriers are selected in accordance to the form of thepreparation, but include for example, starch, lactose,hydroxypropylcellulose, hydroxypropylmethylcellulose,polyvinylpyrrolidone, aluminum stearate, magnesium stearate, etc.

In regards to oral administration, the preparation is administered inthe conventional administration form, for example tablets, capsules,syrups, or suspensions.

In regard to parenteral administration, the compound is prepared intosolutions, emulsions, suspensions etc., and administered in the form ofinjections, or in the form of suppositories, transdermal formulations orpropellants.

Furthermore, the compound may be administered in the form of sustainedrelease preparations.

Such preparations as mentioned above are prepared by admixing knowncarriers, fillers, binders or stabilizing agents with an activeingredient by a conventional method.

In case of preparing injections, buffer agents, solubilizing agents,tonicity agents, etc. may be added to them.

Dose and number of administration vary with a disease to be treated,situation of a patient in question, age, weight, sex, rout ofadministration and a kind of preparations. When the preparation isorally administered, an active ingredient is administered generallyabout 1-1000 mg per day, preferably about 10-500 mg, once or dividedinto several times. In case of injections, an active ingredient isadministered generally about 0.1-500 mg per day, preferably about 3-100mg, once or divided into several times.

The interferon inducer of the present invention can be used astherapeutic or prophylactic agents such as antivirus agents, anticanceragents or agents for anti immunologic disease. The route ofadministration is oral or parenteral as mentioned above.

EXAMPLE

The examples and reference examples are illustrated as follows. However,the scope of the present invention should not be limited to theseexamples.

Example 1 6-Amino-9-benzyl-8-hydroxy-2-methylthiopurine

6-Amino-9-benzyl-8-bromo-2-methylthiopurine (10 mg, 0.026 mmol) inconcentrated hydrochloric acid (10 ml) was refluxed for 4 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (8 mg, yield 96%).

¹H-NMR (DMSO-d₆) δ: 9.60 (1H, br s), 7.31 (5H, m), 6.53 (2H, br s), 4.88(2H, s), 2.42 (3H, s).

Example 2 6-Amino-9-benzyl-2-ethylthio-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-ethylthiopurine (25 mg, 0.069 mmol) inconcentrated hydrochloric acid (25 ml) was refluxed for 4 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (6 mg, yield 29%). ¹H-NMR (DMSO-d6) δ: 10.09(1H, br s), 7.31 (5H, m), 6.51 (2H, br s), 4.88 (2H, s), 2.97 (2H, q,J=7.3 Hz), 1.25 (3H, t, J=7.3 Hz).

Example 3 6-Amino-9-benzyl-8-hydroxy-2-(propylthio)purine

6-Amino-9-benzyl-8-bromo-2-(propylthio)purine (33 mg, 0.087 mmol) inconcentrated hydrochloric acid (35 ml) was refluxed for 2 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (24 mg, yield 87%).

¹H-NMR (DMSO-d₆) δ: 10.19 (1H, br s), 7.31 (5H, m), 6.55 (2H, br s),4.87 (2H, s), 2.98 (2H, t, J=6.9 Hz), 1.61 (2H, m), 0.94 (3H, t, J=7.2Hz).

Example 4 6-Amino-9-benzyl-8-hydroxy-2-(isopropylthio)purine

6-Amino-9-benzyl-8-bromo-2-(isopropylthio)purine (15 mg, 0.040 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 2 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (10 mg, yield 79%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.32 (5H, m), 6.50 (2H, br s), 4.87(2H, s), 3.78 (1H, m), 1.30 (6H, d, J=6.9 Hz).

Example 5 6-Amino-9-benzyl-2-(butylthio)-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-(butylthio)purine (23 mg, 0.059 mmol) inconcentrated hydrochloric acid (10 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (14 mg, yield 99%).

¹H-NMR (DMSO-d₆) δ: 10.05 (1H, br s), 7.30 (5H, m), 6.50 (2H, br s),4.88 (2H, s), 3.00 (2H, t, J=7.0 Hz), 1.58 (2H, m), 1.35 (2H, m), 0.86(3H, t, J=7.2 Hz).

Example 6 6-Amino-9-benzyl-8-hydroxy-2-(isobutylthio)purine

6-Amino-9-benzyl-8-bromo-2-(isobutylthio)purine (21 mg, 0.053 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (16 mg, yield 91%).

¹H-NMR (DMSO-d₆) δ: 10.10 (1H, s), 7.26-7.35 (5H, m), 6.51 (2H, br s),4.87 (2H, s), 2.93 (2H, d, J=6.6 Hz), 1.83(1H, m), 0.93 (6H, d, J=6.6Hz).

Example 7 6-Amino-9-benzyl-8-hydroxy-2-(sec-butylthio)purine

6-Amino-9-benzyl-8-bromo-2-(sec-butylthio)purine (39 mg, 0.092 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 2 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (12 mg, yield 40%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, br s), 7.24-7.35 (5H, m), 6.50 (2H, brs), 4.87 (2H, s), 3.65 (1H, m), 1.61 (2H, m), 1.28 (3H, d, J=7.0 Hz),0.93 (3H, t, J=7.3 Hz).

Example 8 6-Amino-9-benzyl-hydroxy-2-(pentylthio)purine

6-Amino-9-benzyl-8-bromo-2-(pentylthio)purine (39 mg, 0.096 mmol) inconcentrated hydrochloric acid (35 ml) was refluxed for 2.5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (30 mg, yield 91%).

¹H-NMR (DMSO-d₆) δ: 10.05 (1H, br s), 7.30 (5H, m), 6.50 (2H, br s),4.88 (2H, s), 2.99 (2H, t, J=7.3 Hz), 1.59 (2H, m), 1.30 (4H, m), 0.84(3H, t, J=7.3 Hz).

Example 9 6-Amino-9-benzyl-8-hydroxy-2-13-methylbutylthio) purine

6-Amino-9-benzyl-8-bromo-2-(3-methylbutylthio)purine (11 mg, 0.027 mmol)in concentrated hydrochloric acid (20 ml) was refluxed for 3 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (7 mg, yield 75%).

¹H-NMR (DMSO-d₆) δ: 10.10 (1H, br s), 7.30 (5H, m), 6.50 (2H, br s),4.88 (2H, s), 3.00 (2H, t, J=7.6 Hz) 1.63 (1H, m), 1.51 (2H, m), 0.86(6H, t, J=6.2 Hz).

Example 10 6-Amino-9-benzyl-8-hydroxy-2-(2-methylbutylthio)purine

6-Amino-9-benzyl-8-bromo-2-(2-methylbutylthio)purine (29 mg, 0.071 mmol)in concentrated hydrochloric acid (20 ml) was refluxed for 3 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (6 mg, yield 25%).

¹H-NMR (DMSO-d₆) δ: 10.08 (1H, s), 7.30 (5H, m), 6.50 (2H, br s), 4.88(2H, s), 3.08 (1H, q, J=6.6 Hz), 2.86 (1H, m), 1.62 (1H, m), 1.43 (1H,m), 1.15 (1H, m), 0.91 (3H, d, J=6.6 Hz), 0.86 (3H, t, J=6.2 Hz).

Example 11 6-Amino-9-benzyl-2-cyclohexylthio-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-cyclohexylthiopurine (20 mg, 0.048 mmol) inconcentrated hydrochloric acid (10 ml) was refluxed for 6 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (12 mg, yield 70%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, br s), 7.31 (5H, m), 6.49 (2H, br s),4.87 (2H, s), 3.62 (1H, m), 2.00 (2H, m), 1.68 (2H, m), 1.62-1.56 (1H,m), 1.35 (5H, m).

Example 12 6-Amino-9-benzyl-8-hydroxy-2-phenylthiopurine

6-Amino-9-benzyl-8-bromo-2-phenylthiopurine (31 mg, 0.075 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 12 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (11 mg, yield 42%).

¹H-NMR (DMSO-d₆) δ: 9.50 (1H, br s), 7.55 (2H, m), 7.46 (3H, m), 7.28(3H, m), 7.13 (2H, m), 6.55 (2H, br s), 4.67 (2H, s).

Example 13 6-Amino-9-benzyl-8-hydroxy-2-(p-tolylthio)purine

6-Amino-9-benzyl-8-bromo-2-(p-tolylthio)purine (15 mg, 0.035 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 7.5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (5 mg, yield 39%).

¹H-NMR (DMSO-d₆) δ: 7.44 (2H, d, J=7.9 Hz), 7.27 (5H, m), 7.13 (2H, m),6.51 (2H, br s), 4.67 (2H, s), 2.35 (3H, s).

Example 14 6-Amino-9-benzyl-8-hydroxy-2-(2-naphthylthio)purine

6-Amino-9-benzyl-8-bromo-2-(2-naphthylthio)purine (33 mg, 0.043 mmol) ina mixture of concentrated hydrochloric acid (20 ml) and dimethylsulfoxide (7 ml) was refluxed for 6 hours under heating. The reactionmixture was made basic with 28% aqueous ammonia, and the resultingcrystals were filtered, washed with water and the crude product waspurified by thin-layer chromatography to give the subject compound (6mg, yield 35%).

¹H-NMR (DMSO-d₆) δ: 10.14 (1H, br s), 8.30 (1H, d, J=8.6 Hz), 7.98-8.07(2H, m), 7.67-7.77 (3H, m), 7.12-7.20 (3H, m), 6.69 (2H, d, J=6.9 Hz),6.59 (2H, br s), 4.58 (2H, s).

Example 15 6-Amino-9-benzyl-2-benzylthio-8-hydroxypurine

6-Amino-9-benzyl-2-benzylthio-8-bromopurine (18 mg, 0.042 mmol) inconcentrated hydrochloric acid (10 ml) was refluxed for 9 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia,and the resulting crystals were filtered, washed with water and dried togive the subject compound (8 mg, yield 52%).

¹H-NMR (DMSO-ds) δ: 10.12 (1H, br s), 7.19-7.34 (10H, m), 6.58 (2H, brs), 4.91 (2H, s), 4.29 (2H, s).

Example 16 6-Amino-9-benzyl-8-hydroxy-2-methoxypurine

6-Amino-9-benzyl-2,8-dimethoxypurine (53 mg, 0.186 mmol) in concentratedhydrochloric acid (10 ml) was stirred for 3 hours at room temperature.The reaction mixture was made basic with 28% aqueous ammonia, and theresulting crystals were filtered and washed with water to give thesubject compound (38 mg, yield 75%).

¹H-NMR (DMSO-d₆) δ: 9.95 (1H, br s), 7.35-7.22 (5H, m), 6.50 (2H, br s),4.86 (2H, s), 3.76 (3H, s).

Example 17 6-Amino-9-benzyl-2-ethoxy-8-hydroxypurine

6-Amino-9-benzyl-2-ethoxy-8-methoxypurine (18 mg, 0.06 mmol) inconcentrated hydrochloric acid (5 ml) was stirred for 3 hours at roomtemperature. The reaction mixture was made basic with 28% aqueousammonia, and the resulting crystals were filtered and washed with waterto give the subject compound (11 mg, yield 64%).

¹H-NMR (DMSO-d₆) δ: 9.96 (1H, br s), 7.35-7.23 (5H, m), 6.45 (2H, br s),4.85 (2H, s), 4.19 (2H, q, J=7.1 Hz), 1.25 (3H, t, J=7.1 Hz).

Example 18 6-Amino-9-benzyl-8-hydroxy-2-propoxypurine

6-Amino-9-benzyl-8-methoxy-2-propoxypurine (75 mg, 0.24 mmol) inconcentrated hydrochloric acid (15 ml) was stirred for 3 hours at roomtemperature. The reaction mixture was made basic with 28% aqueousammonia, and the resulting crystals were filtered and washed with waterto give the subject compound (59 mg, yield 83%).

¹H-NMR (DMSO-d) δ: 9.96 (1H, br s), 7.35-7.22 (5H, m), 6.45 (2H, br s),4.86 (2H, s), 4.10 (2H, t, J=6.8 Hz), 1.65 (2H, m), 0.93 (3H, t, J=7.3Hz).

Example 19 6-Amino-9-benzyl-2-butoxy-8-hydroxypurine

6-Amino-9-benzyl-2-butoxy-8-methoxypurine (20 mg, 0.061 mmol) inconcentrated hydrochloric acid (5 ml) was stirred for 3 hours at roomtemperature. The reaction mixture was made basic with 28% aqueousammonia. The resulting crystals were filtered, washed with water, andthe crude product was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (13 mg, yield 68%).

¹H-NMR (DMSO-d₆) δ: 9.95 (1H, br s), 7.35-7.23 (5H, m), 6.45 (2H, br s),4.86 (2H, s), 4.13 (2H, t, J=6.4 Hz), 1.62 (2H, m), 1.37 (2H, m), 0.90(3H, t, J=7.3 Hz).

Example 20 6-Amino-9-benzyl-8-hydroxy-2-pentoxypurine

6-Amino-9-benzyl-8-methoxy-2-pentoxypurine (40 mg, 0.117 mmol) inconcentrated hydrochloric acid (20 ml) was stirred for 12 hours at roomtemperature. The reaction mixture was made basic with 28% aqueousammonia. The resulting crystals were filtered and washed with water togive the subject compound (33 mg, yield 86%).

¹H-NMR (DMSO-d₆) δ: 9.97 (1H, br s), 7.35-7.24 (5H, m), 6.44 (2H, br s),4.85 (2H, s), 4.13 (2H, t, J=6.6 Hz), 1.62 (2H, m), 1.32 (4H, m), 0.88(3H, t, J=6.4 Hz).

Example 21 6-Amino-9-benzyl-8-hydroxy-2-methylaminopurine

6-Amino-9-benzyl-8-bromo-2-methylaminopurine (55 mg, 0.17 mmol) inconcentrated hydrochloric acid (30 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (42 mg, yield 94%).

¹H-NMR (DMSO-d₆) δ: 9.67 (1H, br s), 7.31-7.24 (5H, m), 6.19 (1H, q,J=4.8 Hz), 6.06 (2H, br s), 4.81 (2H, s), 2.69 (3H, d, J=4.8 Hz).

Example 22 6-Amino-9-benzyl-2-ethylamino-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-ethylaminopurine (55 mg, 0.16 mmol) inconcentrated hydrochloric acid (30 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (45 mg yield: quantitatively).

¹H-NMR (DMSO-d₆) δ: 9.65 (1H, br s), 7.34-7.24 (5H, m), 6.18 (1H, t,J=5.55 Hz), 6.01 (2H, br s), 4.81 (2H, s), 3.19 (2H, m), 1.06 (3H, t,J=7.1 Hz).

Example 23 6-Amino-9-benzyl-8-hydroxy-2-propylaminopurine

6-Amino-9-benzyl-8-bromo-2-propylaminopurine (86 mg, 0.24 mmol) inconcentrated hydrochloric acid (30 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (69 mg, yield 97%).

¹H-NMR (DMSO-d₆) δ: 9.64 (1H, br s), 7.34-7.24 (5H, m), 6.22 (1H, t,J=5.5 Hz), 6.00 (2H, br s), 4.80 (2H, s), 3.12 (2H, m), 1.46 (2H, m),0.85 (3H, t, J=7.5 Hz).

Example 24 6-Amino-9-benzyl-2-butylamino-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-butylaminopurine (78 mg, 0.21 mmol) inconcentrated hydrochloric acid (30 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (54 mg, yield 83%).

¹H-NMR (DMSO-d₆) δ: 9.64 (1H, br s), 7.29-7.24 (5H, m), 6.19 (1H, t,J=6.2 Hz), 6.00 (2H, br s), 4.80 (2H, s), 3.15 (2H, m), 1.43 (2H, m),1.28 (2H, m), 0.87 (3H, t, J=7.3 Hz).

Example 25 6-Amino-9-benzyl-8-hydroxy-2-pentylaminopurine

6-Amino-9-benzyl-8-bromo-2-pentylaminopurine (74 mg, 0.19 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (36 mg, yield 58%).

¹H-NMR (DMSO-ds) δ: 9.63 (1H, br s), 7.30-7.24 (5H, m), 6.19 (1H, t,J=5.3 Hz), 5.99 (2H, br s), 4.80 (2H, s), 3.19-3.11 (2H, m), 1.48-1.43(2H, m), 1.27-1.24 (4H, m), 0.85 (3H, t, J=7.0 Hz).

Example 26 6-Amino-9-benzyl-8-hydroxy-2-(isopropylamino)purine

6-Amino-9-benzyl-8-bromo-2-(isopropylamino)purine (68 mg, 0.19 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (50 mg, yield 89%).

¹H-NMR (DMSO-d₆) δ: 9.64 (1H, br s), 7.34-7.21 (5H, m), 5.99 (2H, br s),5.98 (1H, d, J=8.2 Hz), 4.80 (2H, s), 4.00-3.90 (1H, m), 1.08 (6H, d,J=6.4 Hz).

Example 27 6-Amino-9-benzyl-8-hydroxy-2-(isobutylamino)purine

6-Amino-9-benzyl-8-bromo-2-(isobutylamino)purine (55 mg, 0.19 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (30 mg, yield 52%).

¹H-NMR (DMSO-d₆) δ: 9.63 (1H, br s), 7.30-7.22 (5H, m), 6.24 (1H, t,J=6.0 Hz), 5.99 (2H, br s), 4.80 (2H, s), 2.99 (2H, dd, J=6.0, 6.0 Hz),1.84-1.75 (1H, m), 0.84 (6H, d, J=6.8 Hz).

Example 28 6-Amino-9-benzyl-8-hydroxy-2-(sec-butylamino)purine

6-Amino-9-benzyl-8-bromo-2-(sec-butylamino)purine (50 mg, 0.13 mmol) inconcentrated hydrochloric acid (20 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (23 mg, yield 55%).

¹H-NMR (DMSO-d₆) δ: 9.63 (1H, br s), 7.31-7.24 (5H, m), 5.97 (2H, br s),5.95 (1H, d, J=8.6 Hz), 4.80 (2H, s), 3.82-3.74 (1H, m), 1.51-1.34 (2H,m), 1.04 (3H, d, J=6.4 Hz), 0.83 (3H, t, J=7.3 Hz).

Example 29 6-Amino-9-benzyl-2-(2.2-dimethylpropyl)amino-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-(2,2-dimethylpropyl)aminopurine (70 mg, 0.18mmol) in concentrated hydrochloric acid (20 ml) was refluxed for 5 hoursunder heating. The reaction mixture was made basic with 28% aqueousammonia. The resulting crystals were filtered, washed with water anddried to give the subject compound (23 mg, yield 39%).

¹H-NMR (DMSO-d₆) δ: 9.63 (1H, br s), 7.28-7.21 (5H, m), 6.04 (1H, t,J=6.2 Hz), 5.97 (2H, br s), 4.79 (2H, s), 3.06 (2H, d, J=6.4 Hz), 0.83(9H, s).

Example 30 6-Amino-9-benzyl-2-benzylamino-8-hydroxypurine

6-Amino-9-benzyl-2-benzylamino-8-bromopurine (37 mg, 0.09 mmol) inconcentrated hydrochloric acid (50 ml) was refluxed for 5 hours underheating. The reaction mixture was made basic with 28% aqueous ammonia.The resulting crystals were filtered, washed with water and dried togive the subject compound (7 mg, yield 23%).

¹H-NMR (DMSO-d₆) δ: 9.75 (1H, br s), 7.31-7.15 (10H, m), 6.83 (1H, t,J=6.4 Hz), 6.10 (2H, br s), 4.78 (2H, s), 4.40 (2H, d, J=6.4 Hz).

Example 31 6-Amino-9-benzyl-2-cyclohexylamino-8-hydroxypurine

6-Amino-9-benzyl-8-bromo-2-cyclohexylaminopurine (82 mg, 0.20 mmol) inconcentrated hydrochloric acid (30 ml) and methanol (20 ml) wererefluxed for 5 hours under heating. After removal of methanol, thereaction mixture was made basic with 28% aqueous ammonia. The resultingcrystals were filtered, washed with water and dried to give the subjectcompound (7 mg, yield 23%).

¹H-NMR (DMSO-d₆) δ: 9.62 (1H, br s), 7.28 (5H, m), 5.96 (3H, br s), 4.78(2H, s), 3.58 (1H, m), 1.80 (2H, m), 1.65 (2H, m), 1.56 (1H, m),1.27-1.06 (5H, m).

Example 32 6-Amino-2-anilino-9-benzyl-8-hydroxypurine

6-Amino-2-anilino-9-benzyl-8-bromopurine (80 mg, 0.20 mmol) inconcentrated hydrochloric acid (200 ml) and methanol (50 ml) wererefluxed for 5 hours under heating. The reaction mixture was condensedin vacuo, 28% aqueous ammonia was added to the residue. The resultingsolid was filtered, washed with water and dried to give the subjectcompound (67 mg yield: quantitatively).

¹H-NMR (DMSO-d₆) δ: 10.00 (1H, Br s), 8.22 (1H, d, J=8.8 Hz), 7.80 (1H,d, J=2.2 Hz), 7.54 (1H, s), 7.47 (1H, dd, J=8.8, 2.2 Hz), 7.35-7.26 (7H,m), 6.45 (2H, br s), 4.89 (2H, s).

Example 33 6-Amino-9-benzyl-2-dimethylamino-8-hydroxypurine

6-Amino-9-benzyl-2-dimethylamino-8-bromopurine (51 mg, 0.15 mmol) inconcentrated hydrochloric acid (30 ml) and methanol (10 ml) wererefluxed for 5 hours under heating. After removal of methanol, thereaction mixture was made basic with 28% aqueous ammonia. The resultingcrystals were filtered, washed with water and dried to give the subjectcompound (38 mg, yield 91%).

¹H-NMR (DMSO-d₆) δ: 9.67 (1H, br s), 7.36-7.24 (5H, m), 6.08 (2H, br s),4.82 (2H, s), 3.01 (6H, s).

Example 34 6-Amino-9-benzyl-2-benzylmethylamino-8-hydroxypurine

6-Amino-9-benzyl-2-benzylmethylamino-8-bromopurine (85 mg, 0.20 mmol) inconcentrated hydrochloric acid (30 ml) and methanol (20 ml) wererefluxed for 5 hours under heating. The reaction mixture was made basicwith 28% aqueous ammonia, and the resulting crystals were filtered,washed with water and dried to give the subject compound (56 mg, yield77%).

¹H-NMR (DMSO-d₆) δ: 9.70 (1H, br s), 7.29-7.19 (10H, m), 6.12 (2H, brs), 4.81 (2H, s), 4.77 (2H, s), 2.99 (3H, s).

Example 35 6-Amino-9-benzyl-8-hydroxy-2-(2-phthalimidoethyl)thiopurine

6-Amino-9-benzyl-8-hydroxy-2-mercaptopurine (120 mg, 0.44 mmol) wassuspended in dimethylformamide (10 ml). To the suspension were addedpotassium carbonate (60 mg, 0.43 mmol) and 2-phthalimidoethyl bromide(112 mg, 0.44 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo and to theresidue was added saturated brine. The mixture was extracted with ethylacetate, the organic layer was dried on magnesium sulfate, and thesolvent was removed in vacuo. Methanol was added to the residue, and theresulting crystals were taken by filtration to give the subject compound(107 mg, yield 54%).

¹H-NMR (DMSO-d₆) δ: 10.19 (1H, br s), 7.83 (4H, m), 7.34 (5H, m), 6.52(2H, br s), 4.96 (2H, s), 3.95 (2H, t, J=6.6 Hz), 3.32 (2H, t, J=6.6Hz).

Example 36 6-Amino-9-benzyl-8-hydroxy-2-(3-phthalimidopropylthio)purine

6-Amino-9-benzyl-8-hydroxy-2-mercaptopurine (110 mg, 0.40 mmol) wassuspended in dimethylformamide (10 ml). To the suspension were addedpotassium carbonate (50 mg, 0.40 mmol) and 2-phthalimidoethyl bromide(108 mg, 0.40 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, water andmethanol were added to the residue, and the resulting crystals weretaken by filtration to give the subject compound (138 mg, yield 75%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.82 (4H, m), 7.24 (5H, m), 6.50 (2H,br s), 4.82 (2H, s), 3.67 (2H, t, J=6.2 Hz), 3.03 (2H, t, J=6.2 Hz),1.96 (2H, m).

Example 37 6-Amino-9-benzyl-8-hydroxy-2-(4-phthalimidobutylthio)purine

6-Amino-9-benzyl-8-hydroxy-2-mercaptopurine (120 mg, 0.44 mmol) wassuspended in dimethylformamide (10 ml). To the suspension were addedpotassium carbonate (60 mg, 0.43 mmol) and 4-phthalimidobutyl bromide(113 mg, 0.40 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, and water andmethanol were added to the residue, and the resulting crystals weretaken by filtration to give the subject compound (141 mg, yield 74%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, br s), 7.84 (4H, m), 7.29 (5H, m), 6.51(2H, br s), 4.83 (2H, s), 3.56 (2H, t, J=6.3 Hz), 3.03 (2H, t, J=6.9Hz), 1.67 (4H, m).

Example 38 3-[(6-Amino-9-benzyl-8-hydroxy-2-purinyl)thio]propanol

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (100 ml). To the suspension wereadded potassium carbonate (150 mg, 1.1 mmol) and 3-bromo-1-propanol (0.1ml, 1 mmol) in order. The mixture was stirred at room temperature for 4hours. The solvent was removed in vacuo, and the residue was purified bysilica gel chromatography (1% methanol/chloroform) to give the subjectcompound (149 mg, yield 62%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.31 (5H, m), 6.50 (2H, br s), 4.90(2H, s), 4.50 (1H, t, J=5.6 Hz), 3.49 (2H, m), 3.07 (2H, t, J=6.6 Hz),1.75 (2H, m).

Example 396-Amino-9-henzyl-8-hydroxy-2-(methoxycarbonylmethylthio)purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and methyl bromoacetate (0.1 ml,1.1 mmol) in order. The mixture was stirred at room temperature for 2hours. The solvent was removed in vacuo, and the residue was purified bysilica gel chromatography (3% methanol/chloroform) to give the subjectcompound (173 mg, yield 69%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.30 (5H, m), 6.57 (2H, br s), 4.84(2H, s), 3.91 (2H, m), 3.56 (2H, s).

Example 406-Amino-9-benzyl-8-hydroxy-2-[2-(methoxycarbonyl)ethyl]thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and methyl 3-bromopropionate(0.12 ml, 1.1 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (146 mg, yield 56%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.30 (5H, m), 6.57 (2H, br s), 4.84(2H, s), 3.91 (2H, s), 3.56 (2H, s).

Exanple 41 6-Amino-9-benzyl-8-hydroxy-2-(carboxymethylthio)purine

To a methanol solution (5 ml) containing 500 mg of sodium hydroxide wasadded 6-amino-9-benzyl-8-hydroxy-2-(methoxycarbonylmethyl)thiopurine (64mg, 0.19 mmol). The solution was refluxed under heating, neutralizedwith 2N hydrochloric acid, filtered and washed with water to give thesubject compound (32 mg, yield 52%).

¹H-NMR (DMSO-d₆) δ: 10.44 (1H, s), 7.34 (5H, m), 6.64 (2H, br s), 4.85(2H, s), 3.82 (2H, s).

Example 42 6-Amino-9-benzyl-8-hydroxy-2-(methoxymethylthio)purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and chloromethyl methyl ether(0.056 ml, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (2%methanol/chloroform) to give the subject compound (107 mg, yield 69%).

¹H-NMR (DMSO-d₆) δ: 10.15 (1H, s), 7.31 (5H, m), 6.59 (2H, br s), 5.29(2H, s), 4.89 (2H, s), 3.21 (3H, s).

Example 43 6-Amino-9-benzyl-8-hydroxy-2-(2-ethoxyethyl)thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 2-chloroethyl ethyl ether(0.056 ml, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 3 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (1%methanol/chloroform) to give the subject compound (19 mg, yield 11%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.30 (5H, m), 6.54 (2H, br s), 4.88(2H, s), 3.54 (2H, t, J=6.9 Hz), 3.43 (2H, q, J=7.0 Hz), 3.18 (2H, t,J=6.6 Hz), 1.08 (3H, t, J=6.9 Hz).

Example 44 6-Amino-9-benzyl-8-hydroxy-2-[(2-hydroxyethyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 2-bromoethanol (0.052 ml,0.73 mmol) in order. The mixture was stirred at room temperature for 5hours. The solvent was removed in vacuo, and the residue was purified bysilica gel chromatography (2% methanol/chloroform) to give the subjectcompound (72 mg, yield 46%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.32 (5H, m), 6.52 (2H, br s), 4.87(3H, s), 3.59 (2H, q, J=5.9 Hz), 3.12 (2H, t, J=6.6 Hz).

Example 45 [(6-Amino-9-benzyl-8-hydroxy-2-purinyl)thio]acetamide

A 28% ammonia/methanol solution was added to6-amino-9-benzyl-8-hydroxy-2-(methoxycarbonylmethyl)thiopurine (75 mg,0.22 mmol). The solution was heated in autoclave for 6 hours and thenthe solvent was removed in vacuo. To the residue was added methanol andthe resulting crystals were filtered to give the subject compound (64mg, yield 89%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.42 (1H, br s), 7.34 (5H, m), 7.07(1H, br s), 6.57 (2H, br s), 4.87 (2H, s), 3.70 (2H, s).

Example 466-Amino-9-benzyl-2-[(1,3-dioxolan-2-yl)-methyl]thio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and 2-bromomethyl-1,3-dioxolane(0.11 ml, 1.1 mmol) in order. The mixture was stirred at roomtemperature for 3 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (73 mg, yield 28%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.31 (5H, m), 6.57 (2H, br s), 5.03(1H, t, J=4.6 Hz), 4.87 (2H, s), 3.92 (2H, m), 3.78 (2H, m), 3.28 (2H,d, J=5.0 Hz).

Example 476-Amino-9-benzyl-8-hydroxy-2-[2-(dimethylamino)ethyl)thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (300 mg, 2.2 mmol) and 2-dimethylaminoethylchloride(160 mg, 1.1 mmol) in order. The mixture was stirred at room temperaturefor 11 hours. The solvent was removed in vacuo, and the residue waspurified by silica gel chromatography (10% methanol/chloroform) to givethe subject compound (9 mg, yield 4%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.29 (5H, m), 6.53 (2H, br s), 4.88(2H, s), 3.11 (2H, t, J=7.6 Hz), 2.14 (6H, s).

Example 48 6-Amino-9-benzyl-8-hydroxy-2-[(2-methoxyethyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 2-chloroethyl methyl ether(0.067 ml, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 8 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (20 mg, yield 12%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.30 (5H, m), 6.55 (2H, br s), 4.87(2H, s), 3.50 (2H, t, J=6.6 Hz), 3.22 (3H, m), 3.21 (2H, t, J=6.6 Hz).

Example 49 6-Amino-9-benzyl-8-hydroxy-2-(formylmethylthio)purine

6-Amino-9-benzyl-2-(1,3-dioxolan-2-yl-methyl)thio-8-hydroxypurine (44mg, 0.12 mmol) was dissolved in a mixture of 3.3N hydrochloric acid (1ml) and tetrahydrofuran (4 ml). The solution was stirred at 70° C. for 7hours and then neutralized with aqueous sodium hydrogen carbonate. Afterremoval of tetrahydrofuran in vacuo, the resulting crystals werefiltered, washed with water and repulped in methanol to give the subjectcompound (17 mg, yield 44%).

¹H-NMR (DMSO-d₆) δ: 10.14 (1H, br s), 9.52 (1H, s), 7.31 (5H, m), 6.60(2H, br s), 3.81 (2H, s).

Example 50 6-Amino-9-benzyl-8-hydroxy-2-(2-morpholinoethyl)thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 4-(2-chloroethyl)morpholine(136 mg, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 8 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (8%methanol/chloroform) to give the subject compound (34 mg, yield 18%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.28 (511, m), 6.53 (2H, br s), 3.51(4H, m), 3.11 (2H, t, J=7.6 Hz), 2.34 (4H, m).

Example 516-Amino-9-benzyl-2-[2-(1,3-dioxolan-2-yl)ethylthio)-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and2-(2-bromoethyl)-1,3-dioxolane (0.14 ml, 1.1 mmol) in order. The mixturewas stirred at room temperature for 3 hours. The solvent was removed invacuo, and the residue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (163 mg, yield 60%).

¹H-NMR (DMSO-d₆) δ: 10.10 (1H, s), 7.34 (5H, m), 6.52 (2H, br s), 4.89(1H, t, J=4.3 Hz), 4.87 (2H, s), 3.89 (2H, m), 3.77 (2H, m), 3.05 (2H,t, J=6.9 Hz), 1.96 (2H, m).

Example 52 6-Amino-9-benzyl-2-(2-formylethylthio)-8-hydroxypurine

6-Amino-9-benzyl-2-[2-(1,3-dioxolan-2-yl)ethyl)thio-8-hydroxypurine (74mg, 0.20 mmol) was dissolved in a mixture of 3.3N hydrochloric acid (1ml) and tetrahydrofuran (4 ml). The solution was stirred at 70° C. for 7hours and then neutralized with aqueous sodium hydrogen carbonate. Afterremoval of tetrahydrofuran in vacuo, the resulting crystals werefiltered, purified by silica gel chromatography (5% methanol/chloroform)to give the subject compound (17 mg, yield 44%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 9.64 (1H, s), 7.30 (5H, m), 6.55 (2H,br s), 4.86 (2H, s), 3.02 (2H, t, J=6.9 Hz), 2.82 (2H, t, J=7.0 Hz).

Example 53 6-Amino-9-benzyl-8-hydroxy-2-[(2-carboxyethyllthio]purineAcid

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (300 mg, 2.2 mmol) and 3-iodopropionic acid (220 mg,1.1 mmol) in order. The mixture was stirred at room temperature for 3hours. The solvent was removed in vacuo, and the residue was purified bysilica gel chromatography (20% methanol/chloroform) to give the subjectcompound (38 mg, yield 15%).

¹H-NMR (DMSO-d₆) δ: 12.27 (1H, s), 10.12 (5H, m), 7.31 (5H, m), 6.55(2H, br s), 4.87 (2H, s), 3.17 (2H, t, J=6.6 Hz), 2.62 (2H, t, J=6.6Hz).

Example 546-Amino-9-benzyl-8-hydroxy-2-[(2,2,2-trifluoroethyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.7 mmol) and 2-iodo-1,1,1-trifluoroethane(0.07 ml, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 8 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (20 mg, yield 12%).

¹H-NMR (DMSO-d₆) δ: 10.19 (1H, s), 7.31 (5H, m), 6.70 (2H, br s), 4.90(2H, s), 4.16 (2H, q, J=10.5 Hz).

Example 55 6-Amino-9-benzyl-2-[(2-fluoroethyl)thio]-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 1-bromo-2-fluoroethane (0.05ml, 0.7 mmol) in order. The mixture was stirred at room temperature for4 hours. The solvent was removed in vacuo, and the residue was purifiedby silica gel chromatography (3% methanol/chloroform) to give thesubject compound (100 mg, yield 64%).

¹H-NMR (DMSO-d₆) δ: 10.14 (1H, s), 7.31 (5H, m), 6.59 (br s), 4.88 (2H,s), 4.63 (1H, t, J=6.6 Hz), 4.46 (1H, t, J=6.6 Hz), 3.31 (4H, m).

Example 56 6-Amino-9-benzyl-2-[(4-chlorobenzyl)thio]-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 _mg, 0.49 mmol)was suspended in dimethylformamide (65 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 4-chlorobenzyl chloride (130mg, 0.81 mmol) in order. The mixture was stirred at room temperature for8 hours. The solvent was removed in vacuo, and the residue was purifiedby silica gel chromatography (5% methanol/chloroform) to give thesubject compound (74 mg, yield 38%).

¹H-NMR (DMSO-d₆) δ: 10.13 (1H, s), 7.29 (9H, m), 6.59 (2H, br s), 4.91(2H, s), 4.26 (s, 2H).

Example 57 6-Amino-9-benzyl-8-hydroxy-2-[(3-methoxybenzyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 3-methoxybenzyl chloride(0.1 ml, 0.7 mmol) in order. The mixture was stirred at room temperaturefor 2 hours. The solvent was removed in vacuo, and the residue waspurified by silica gel chromatography (5% methanol/chloroform) to givethe subject compound (94 mg, yield 49%).

¹H-NMR (DMSO-d₆) δ: 10.13 (1H, s), 7.28 (5H, m), 7.15 (1H, m), 6.96 (2H,m), 6.79 (1H, m), 6.59 (2H, br s), 4.89 (2H, s), 4.27 (2H, s), 3.68 (3H,s).

Example 58 6-Amino-9-benzyl-2-cyclohexylmethylthio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and cyclohexylmethyl bromide(0.1 ml, 0.7 mmol) in order. The mixture was stirred at room temperaturefor 9 hours. The solvent was removed in vacuo, and the residue waspurified by silica gel chromatography (3% methanol/chloroform) to givethe subject compound (93 mg, yield 51%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.30 (5H, m), 6.50 (2H, br s), 4.87(2H, s), 2.93 (2H, d, J=6.6 Hz), 1.78-0.88 (11H, m).

Example 59 6-Amino-9-benzyl-2-[(3-dimethylaminopropyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (200 mg, 1.44 mmol) and 3-dimethylaminopropylchloride hydrochloride (114 mg, 0.72 mmol) in order. The mixture wasstirred at room temperature for 9 hours. The solvent was removed invacuo, and the residue was purified by silica gel chromatography (14%methanol/chloroform) to give the subject compound (13 mg, yield 7%).

¹H-NMR (DMSO-d₆) δ: 10.10 (1H, s), 7.30 (5H, m), 6.50 (2H, br s), 4.87(2H, s), 3.00 (2H, t, J=7.6 Hz), 2.26 (2H, t, J=7.3 Hz), 2.08 (6H, S),1.72 (2H, m).

Example 60 3-(6-Amino-9-benzyl-8-hydroxy-2-purinyl)thio-1-propanol

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 3-bromo-1-propanol (0.07 ml,0.7 mmol) in order. The mixture was stirred at room temperature for 3hours. The solvent was removed in vacuo, and the residue was purified bysilica gel chromatography (4% methanol/chloroform) to give the subjectcompound (64 mg, yield 39%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.31 (5H, m), 6.51 (2H, br s), 4.87(2H, s), 4.51 (1H, t, J=5.3 Hz), 3.48 (2H, q, J=5.6 Hz), 3.05 (2H, t,J=6.9 Hz), 1.75 (211, m).

Example 61 6-Amino-9-benzyl-2-(3-chlorobenzyl)thio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 3-chlorobenzyl chloride(0.09 ml, 0.7 mmol) in order. The mixture was stirred at roomtemperature for 5 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (92 mg, yield 47%).

¹H-NMR (DMSO-d₆) δ: 10.14 (1H, s), 7.45 (1H, m), 7.27 (5H, m), 6.61 (2H,br s), 4.90 (2H, s), 4.30 (2H, s).

Example 626-Amino-9-benzyl-8-hydroxy-2-[3-(methoxycarbonyl)propyl]-thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (200 mg, 0.73 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and methyl 4-chlorobutylate (0.13ml, 1.1 mmol) in order. The mixture was stirred at room temperature for3 hours. The solvent was removed in vacuo, and the residue was purifiedby silica gel chromatography (2% methanol/chloroform) to give thesubject compound (97 mg, yield 36%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.30 (5H, m), 6.53 (2H, br s), 4.88(2H, s), 3.57 (3H, s), 3.03 (2H, t, J=7.2 Hz), 2.39 (2H, t, J=7.2 Hz),1.86 (2H, m).

Example 63 6-Amino-9-benzyl-8-hydroxy-2-[(2-phenylethyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 2-bromoethylbenzene (0.10ml, 0.73 mmol) in order. The mixture was stirred at room temperature for4 hours. The solvent was removed in vacuo, and the residue was purifiedby silica gel chromatography (3% methanol/chloroform) to give thesubject compound (117 mg, yield 63%).

¹H-NMR (DMSO-d₆) δ: 10.13 (1H, s), 7.28 (5H, m), 6.56 (2H, br s), 4.92(2H, s), 3.22 (2H, m), 2.89 (2H, t, J=6.6 Hz).

Example 64 4-(6-Amino-9-benzyl-8-hydroxy-2-purinyl)thiobutyric Acid

To a methanol solution (5 ml) containing 500 mg of sodium hydroxide wasadded 6-amino-9-benzyl-8-hydroxy-2-[(methoxycarbonylpropyl)]thiopurine(60 mg, 0.16 mmol). The solution was refluxed under heating for 5 hours,and neutralized with 2N hydrochloric acid and then aqueous sodiumhydrogen carbonate. After removal of the solvent in vacuo, the resultingcrystals were filtered and washed with water to give the subjectcompound (5 mg, yield 9%).

¹H-NMR (DMSO-d₆) δ: 7.31 (5H, m), 6.90 (2H, br s), 3.02 (2H, m), 2.09(2H, m), 1.79 (2H, m).

Example 65 6-Amino-9-benzyl-8-hydroxy-2-[(4-methoxybenzyl)thio]purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 4-methoxybenzyl chloride(0.098 ml, 0.72 mmol) in order. The mixture was stirred at roomtemperature for 3 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (80 mg, yield 41%).

¹H-NMR (DMSO-d₆) δ: 10.13 (1H, s), 7.28 (5H, m), 6.73 (2H, t, J=8.9 Hz),6.57 (2H, br s), 4.92 (2H, s), 4.22 (2H, s), 3.69 (3H, s).

Example 66 6-Amino-9-benzyl-2-(2-cyanoethyl)thio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 3-chloropropionitrile (65mg, 0.73 mmol) in order. The mixture was stirred at room temperature for3 hours. The solvent was removed in vacuo, and to the residue was addedwater. The mixture was extracted with chloroform and the organic layerwas dried on sodium sulfate. After removal of the solvent in vacuo, theresidue was purified by silica gel chromatography (5%methanol/chloroform) to give the subject compound (72 mg, yield 45%).

¹H-NMR (DMSO-d₆) δ: 10.17 (1H, br s), 7.36-7.25 (5H, m), 6.63 (2H, brs), 4.90 (2H, s), 3.24 (2H, t, J=6.0 Hz), 2.88 (2H, t, J=6.0 Hz).

Example 67 6-Amino-9-benzyl-2-cyanomethylthio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (150 mg, 0.55 mmol)was suspended in dimethylformamide (10 ml). To the suspension were addedpotassium carbonate (81 mg, 0.59 mmol) and chloroacetonitrile (44 mg,0.59 mmol) in order. The mixture was stirred at room temperature for 3hours. The solvent was removed in vacuo, and to the residue was addedwater. The mixture was extracted with chloroform and the organic layerwas dried on sodium sulfate. After removal of the solvent in vacuo, theresidue was purified by silica gel chromatography (1% ammonia, 5%methanol/chloroform) to give the subject compound (58 mg, yield 25%).

¹H-NMR (DMSO-d₆) δ: 10.21 (1H, br s), 7.41-7.24 (5H, m), 6.71 (2H, brs), 4.91 (2H, s), 4.15 (2H, s).

Example 68 6-Amino-9-benzyl-2-(3-cyanopropyl)thio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (150 mg, 0.55 mmol)was suspended in dimethylformamide (10 ml). To the suspension were addedpotassium carbonate (202 mg, 1.46 mmol) and 4-chlorobutyronitrile (152mg, 1.46 mmol) in order. The mixture was stirred at room temperature for3 hours. The solvent was removed in vacuo, and to the residue was addedwater. The mixture was extracted with chloroform and the organic layerwas dried on sodium sulfate. After removal of the solvent in vacuo, theresidue was purified by silica gel chromatography (5%methanol/chloroform) to give the subject compound (71 mg, yield 29%).

¹H-NMR (DMSO-d₆) δ: 10.13 (1H, br s), 7.36-7.22 (5H, m), 6.55 (2H, brs), 4.91 (2H, s), 3.08 (2H, t, J=7.0 Hz), 2.56 (2H, t, J=7.0 Hz), 1.91(2H, m).

Example 69 6-Amino-9-benzyl-8-hydroxy-2-(4-methylthiomethyl)thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and chloromethyl methyl sulfide(0.06 ml, 0.72 mmol) in order. The mixture was stirred at roomtemperature for 4 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (83 mg, yield 51%).

¹H-NMR (DMSO-d₆) δ: 10.14 (1H, s), 7.33 (5H, m), 6.59 (2H, br s), 4.88(2H, s), 4.30 (2H, s), 2.11 (3H, s).

Example 70 6-Amino-9-benzyl-2-(benzyloxymethyl)thio-8-hydroxypurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and benzyloxymethyl chloride(0.1 ml, 0.7 mmol) in order. The mixture was stirred at room temperaturefor 4 hours. The solvent was removed in vacuo, and the residue waspurified by silica gel chromatography (3% methanol/chloroform) to givethe subject compound (90 mg, yield 47%).

¹H-NMR (DMSO-d₆) δ: 10.15 (1H, s), 7.30 (10H, m), 6.61 (2H, br s), 4.88(2H, s), 4.52 (2H, s).

Example 716-Amino-9-benzyl-8-hydroxy-2-[3-(1-piperazinyl)propyl]thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and 1-(3-chloropropyl)piperazine(179 mg, 0.73 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (20%methanol/chloroform) to give the subject compound (10 mg, yield 5%).

¹H-NMR (DMSO-d₆) δ: 7.31 (5H, m), 6.62 (2H, br s), 4.87 (2H, s),3.04-2.94 (6H, m), 2.43-2.37 (6H, m), 1.76 (2H, m).

Example 72 6-Amino-9-benzyl-8-hydroxy-2-[2-(methylthio)ethyl]thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (100 mg, 0.72 mmol) and chloromethyl ethyl sulfide(0.08 ml, 0.7 mmol) in order. The mixture was stirred at roomtemperature for 2 hours. The solvent was removed in vacuo, and theresidue was purified by silica gel chromatography (3%methanol/chloroform) to give the subject compound (28 mg, yield 16%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.31 (5H, m), 6.54 (2H, br s), 4.88(2H, s), 3.21 (2H, m), 2.73 (2H, m), 2.07 (3H, s).

Example 73 4-[(6-Amino-9-henzyl-8-hydroxy-2-purinyl)thio]butanol

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (470 mg, 1.7 mmol) wassuspended in dimethylformamide (80 ml). To the suspension were addedpotassium carbonate (350 mg, 2.5 mmol) and 4-chlorobutanol (0.25 ml, 2.5mmol) in order. The mixture was stirred at room temperature for 4 hours.The solvent was removed in vacuo, and the residue was purified by silicagel chromatography (7% methanol/chloroform) to give the subject compound(29 mg, yield 5%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.31 (5H, m), 6.50 (2H, br s), 4.87(2H, s), 4.40 (1H, t, J=5.3 Hz), 3.39 (2H, q, J=5.3 Hz), 3.02 (2H, t,J=6.9 Hz), 1.67-1.48 (4H, m).

Example 746-Amino-9-benzyl-8-hydroxy-2-{2-(2-methoxyethoxy)ethyl]thio}purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (350 mg, 1.7 mmol) wassuspended in dimethylformamide (100 ml). To the suspension were addedpotassium carbonate (350 mg, 2.5 mmol) and1-(2-chloroethoxy)-2-methoxyethane (1.04 g, 2.6 mmol) in order. Themixture was stirred at room temperature for 2 hours. The solvent wasremoved in vacuo, and the residue was purified by silica gelchromatography (7% methanol/chloroform) to give the subject compound (69mg, yield 11%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.30 (5H, m), 6.54 (2H, br s), 4.88(2H, s), 3.58 (2H, t, J=6.6 Hz), 3.49 (2H, t, J=2.6 Hz), 3.40 (2H, t,J=5.9 Hz), 3.22 (3H, s), 3.18 (2H, t, J=6.6 Hz).

Example 756-Amino-9-benzyl-8-hydroxy-2-{[2-(2-hydroxyethoxy)ethyl]thio}purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (470 mg, 1.7 mmol) wassuspended in dimethylformamide (100 ml). To the suspension were addedpotassium carbonate (350 mg, 2.5 mmol) and 2-(2-chloroethoxy)ethanol(0.27 ml, 2.6 mmol) in order. The mixture was stirred at roomtemperature for 4 hours. The solvent was removed in vacuo and theresidue was purified by silica gel chromatography (7%methanol/chloroform) to give the subject compound (159 mg, yield 27%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.31 (5H, m), 6.54 (2H, br s), 4.88(2H, s), 4.59 (1H, t, J=5.6 Hz), 3.48-3.39 (4H, m), 3.19 (2H, t, J=6.6Hz).

Example 766-Amino-9-benzyl-8-hydroxy-2-{[2-(2-ethoxyethoxy)ethyl]thio}purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (470 mg, 1.7 mmol) wassuspended in dimethylformamide (100 ml). To the suspension were addedpotassium carbonate (350 mg, 2.5 mmol) and1-ethoxy-2-(2-bromoethoxy)ethane (505 mg, 2.6 mmol) in order. Themixture was stirred at room temperature for 2 hours. The solvent wasremoved in vacuo, and the residue was purified by silica gelchromatography (1% methanol/chloroform) to give the subject compound(147 mg, yield 22%).

¹H-NMR (DMSO-d₆) δ: 10.11 (1H, s), 7.31 (5H, m), 6.54 (2H, br s), 4.88(2H, s), 3.58 (2H, t, J=6.9 Hz), 3.51-3.36 (6H, m), 3.18 (2H, t, J=6.9Hz), 1.07 (3H, t, J=6.9 Hz).

Example 77 6-Amino-9-benzyl-8-hydroxy-2-(3-ethoxypropyl)thiopurine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (80 mg, 0.65 mmol) wassuspended in dimethylformamide (60 ml). To the suspension were addedpotassium carbonate (150 mg, 1.1 mmol) and 2-ethoxypropylp-toluenesulfonate (280 mg, 1.1 mmol) in order. The mixture was stirredat room temperature for 4 hours. The solvent was removed in vacuo, andthe residue was purified by silica gel chromatography (5%methanol/chloroform) to give the subject compound (69 mg, yield 30%).

¹H-NMR (DMSO-d₆) δ: 10.09 (1H, s), 7.31 (5H, m), 6.51 (2H, br s), 4.87(2H, s), 3.44-3.34 (4H, m), 3.03 (2H, t, J=8.9 Hz), 1.83 (2H, m), 1.08(3H, t, J=6.9 Hz).

Example 786-Amino-9-benzyl-8-hydroxy-2-{[2-(2-hydroxyethylthio)ethyl]thio}purine

Crude 6-amino-9-benzyl-8-hydroxy-2-mercaptopurine (134 mg, 0.49 mmol)was suspended in dimethylformamide (50 ml). To the suspension were addedpotassium carbonate (100 mg, 0.73 mmol) and 2-(2-chloroethyl)thioethanol(170 mg, 1.2 mmol) in order. The mixture was stirred at room temperaturefor 24 hours. To the reaction mixture were added 2N hydrochloric acidand then 28% aqueous ammonia. The mixture was extracted with chloroform,the organic layer was dried on magnesium sulfate and then the solventwas removed in vacuo. The residue was purified by silica gelchromatography (5% methanol/chloroform) to give the subject compound (17mg, yield 6%).

¹H-NMR (DMSO-d₆) δ: 10.12 (1H, s), 7.31 (5H, m), 6.53 (2H, br s), 4.87(2H, s), 4.82 (1H, t, J=5.6 Hz), 3.53 (2H, t, J=6.6 Hz), 3.18 (2H, m),2.77 (2H, t, J=8.2 Hz), 2.63 (2H, t, J=6.6 Hz).

Example 79 6-Amino-9-benzyl-8-hydroxy-2-(2-methoxyethyl)aminopurine

6-Amino-9-benzyl-8-methoxy-2-(2-methoxyethyl)aminopurine (26 mg, 0.079mmol) in concentrated hydrochloric acid (20 ml) was stirred at roomtemperature for 7 hours. The reaction mixture was made basic with 28%aqueous ammonia. The resulting crystals were filtered to give thesubject compound (18 mg, yield 73%).

¹H-NMR (DMSO-d₆) δ: 9.66 (1H, br s), 7.34-7.26 (5H, m), 6.14 (1H, t,J=4.8 Hz), 6.05 (2H, br s), 4.80 (2H, s), 3.39-3.34 (4H, m), 3.22 (3H,s).

Example 80 6-Amino-9-benzyl-2-(2-ethoxyethoxy)-8-hydroxypurine

6-Amino-9-benzyl-2-(2-ethoxyethoxy)-8-methoxypurine (110 mg, 0.32 mmol)in concentrated hydrochloric acid (20 ml) was stirred at roomtemperature for 12 hours. The reaction mixture was evaporated in vacuoto dryness and then 28% aqueous ammonia was added thereto. The resultingcrystals were filtered to give the subject compound (88 mg, yield 84%).

¹H-NMR (DMSO-d₆) δ: 9.98(1H, br s), 7.35-7.23(5H, m), 6.48(2H, br s),4.86(2H, s), 4.25(2H, t, J=4.6 Hz), 3.62(2H, t, J=4.6 Hz), 3.45(2H, q,J=7.0 Hz), 1.11(3H, t, J=7.0 Hz).

Example 816-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-(2-methoxyethoxy)purine

6-Amino-9-(4-fluorobenzyl)-8-methoxy-2-(2-methoxyethoxy)purine (49 mg,0.14 mmol) in concentrated hydrochloric acid (20 ml) was stirred for 12hours. The reaction mixture was evaporated in vacuo to dryness and then28% aqueous ammonia was added thereto. The resulting crystals werefiltered to give the subject compound (36 mg, yield 77%).

¹H-NMR(DMSO-d₆) δ: 9.97(1H, br s), 7.35(2H, m), 7.14(2H, m), 6.48(2H, brs), 4.84(2H, s), 4.27(2H, t, J=4.6 Hz), 3.59(2H, t, J=4.6 Hz), 3.28(3H,s).

Example 82 6-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-methylthiopurine

6-amino-9-(4-fluorobenzyl)-8-hydroxy-2-mercaptopurine (200 mg, 0.687mmol) was suspended in methanol (20 ml). To the suspension were addedpotassium carbonate (190 mg, 1.37 mmol) and methyl iodide (975 mg, 6.87mmol) in order. The mixture was stirred at room temperature for 30minutes. The reaction mixture were evaporated in vacuo to dryness andextracted with chloroform. The organic layer was dried on sodiumsulfate. After removal of the solvent in vacuo, the residue was purifiedby silica gel chromatography (3% methanol/chloroform) to give thesubject compound (63 mg, yield 30%).

¹H-NMR (DMSO-d₆) δ: 10.11(1H, br s), 7.37(2H, m), 7.15(2H, m), 6.53(2H,br s), 4.87(2H, s), 2.43(3H, s).

Example 83 6-Amino-9-benzyl-2-(3-hydroxypropoxy)-8-hydroxypurine

6-Amino-9-benzyl-2-(3-hydroxypropoxy)-8-methoxypurine (83 mg, 0.25 mmol)in concentrated hydrochloric acid (5 ml) was stirred at room temperaturefor 4 hours. The reaction mixture was neutralized with 28% aqueousammonia and the resulting crystals were filtered and washed with waterto give the subject compound (40 mg, yield 51%).

¹H-NMR(DMSO-d₆) δ: 9.95(1H, br s), 7.30(5H, m), 6.45(2H, br s), 4.85(2H,s), 4.50(1H, t, J=5.0 Hz), 4.20(2H, t, J=6.0 Hz), 3.51(2H, q, J=5.0 Hz),1.79(2H, m).

Example 84 6-Amino-9-benzyl-8-hydroxy-2-(3-ethoxypropoxy)npurine

6-Amino-9-benzyl-2-(3-ethoxypropoxy)-8-methoxypurine (149 mg, 0.417mmol) in concentrated hydrochloric acid (20 ml) was stirred at roomtemperature for 12 hours. The reaction mixture was evaporated in vacuoto dryness and neutralized with 28% aqueous ammonia. The resultingcrystals were filtered to give the subject compound (112 mg, yield 78%).

¹H-NMR(DMSO-d₆) δ: 9.97(1H, br s), 7.31-7.23(5H, m), 6.45(2H, br s),4.84(2H, s), 4.17(2H, t, J=6.6 Hz), 3.44(2H, t, J=6.6 Hz), 3.38(2H, q,J=7.0 Hz), 1.85(2H, m), 1.08(3H, t, J=7.0 Hz).

Example 85 6-Amino-9-benzyl-8-hydroxy-2-(4-hydroxybutoxy)purine

6-Amino-9-benzyl-2-(4-hydroxybutoxy)-8-methoxypurine (114 mg, 0.332mmol) in concentrated hydrochloric acid (20 ml) was stirred at roomtemperature for 12 hours. The reaction mixture was evaporated in vacuoto dryness and to the residue was added aqueous ammonia. The resultingcrystals were filtered to give the subject compound (80 mg, yield 73%).

¹H-NMR(DMSO-d₆) δ: 9.95(1H, br s), 7.33-7.24(5H, m), 6.45(2H, br s),4.85(2H, s), 4.43(1H, t, J=5.1 Hz), 4.14(2H, t, J=6.6 Hz), 3.42(2H, m),1.67(2H, m), 1.50(2H, m).

Example 86 6-Amino-9-benzyl-8-hydroxy-2-(2-methylthioethoxy)purine

6-amino-9-benzyl-2-chloro-8-methoxypurine (190 mg, 0.56 mmol) was addedto 2-methylthioethanol (3 ml) containing sodium (110 mg, 4.78 mmol). Themixture was heated for 2 hours. Thereto were added 2N hydrochloric acidand 28% aqueous ammonia in order. The mixture was extracted with 3%methanol/chloroform and the organic layer was dried on sodium sulfate.After removal of the solvent in vacuo, the residue was purified bysilica gel chromatography (3% methanol/chloroform) to give the subjectcompound (59 mg, yield 27%).

¹H-NMR(DMSO-d₆) δ: 9.97(1H, s), 7.30(5H, m), 6.49(2H, br s), 4.85(2H,s), 4.30(2H, t, J=7.0 Hz), 2.76(2H, t, J=6.9 Hz), 2.10(3H, 5).

Example 87 6-Amino-9-benzyl-8-hydroxy-2-(2-hydroxyethoxy)purine

6-Amino-9-benzyl-2-(2-hydroxyethoxy)-8-methoxypurine (70 mg, 0.22 mmol)in concentrated hydrochloric acid (5 ml) was stirred at room temperaturefor 5 hours. The reaction mixture was neutralized with 28% aqueousammonia and the resulting crystals were filtered and washed with waterto give the subject compound (38 mg, yield 57%).

¹H-NMR(DMSO-d₆) δ: 9.89(1H, br s), 7.30(5H, m), 6.46(2H, br s), 4.85(2H,s), 4.79(1H, t, J=5.6 Hz), 4.15(2H, t, J=4.9 Hz), 3.65(2H, m).

Example 88 6-Amino-9-benzyl-8-hydroxy-2-(2-methoxyethoxy)purine

6-Amino-9-benzyl-8-methoxy-2-(2-methoxyethoxy)purine (21 mg, 0.064 mmol)in concentrated hydrochloric acid (20 ml) was stirred at roomtemperature for 5 hours. The reaction mixture was evaporated in vacuo todryness and 28% aqueous ammonia was added to the residue. The resultingcrystals were filtered and washed with water to give the subjectcompound (17 mg, yield 84%).

¹H-NMR(DMSO-d₆) δ: 9.97(1H, br s), 7.35-7.23(5H, m), 6.48(2H, br s),4.86(2H, s), 4.26(2H, t, J 4.6 Hz), 3.58(2H, t, J=4.6 Hz), 3.27(3H, s).

Example 89 6-Amino-2-(2-aminoethylthio)-9-benzyl-8-hydroxypurine

6-Amino-9-benzyl-8-hydroxy-2-(2-phthalimidoethylthio)purine (78 mg, 0.18mmol) was suspended in 1M hydrazine monohydrate (10 ml). The suspensionwas stirred at room temperature for 9 hours. The reaction mixture wasevaporated in vacuo to dryness and to the residue was added 2Nhydrochloric acid. Insoluble materials were filtered off and thefiltrate was neutralized with 28% aqueous ammonia and extracted withethyl acetate. The organic layer was dried on magnesium sulfate andevaporated in vacuo to dryness to give the subject compound (4 mg, yield7%).

¹H-NMR(DMSO-d₆) δ: 7.31(7H, m), 6.53(2H, br s), 4.88(2H, s), 3.05(2H, t,J=6.3 Hz), 2.76(2H, t, J=6.6 Hz).

Example 90 6-Amino-2-butylthio-9-(4-fluorobenzyl)-8-hydroxypurine

6-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-thiopurine (200 mg, 0.687 mmol)and potassium carbonate (190 mg, 1.37 mmol) were dissolved indimethylformamide (10 ml). Butyl bromide (941 mg, 6.87 mnmol) was addedthereto and the mixture was stirred at room temperature for 4 hours. Thereaction mixture was evaporated in vacuo to dryness. Water was added tothe residue and the solution was extracted with chloroform. The organiclayer was dried on magnesium sulfate and evaporated in vacuo to dryness.The residue was purified by silica gel chromatography (2%methanol/chloroform) to give the subject compound (38 mg, yield 16%).

¹H-NMR(DMSO-d₆) δ: 10.10(1H, br s), 7.35(2H, m), 7.14(2H, m), 6.51(2H,br s), 4.87(2H, s), 3.00(2H, t, J=7.1 Hz), 1.56(2H, m), 1.36(2H, m),0.86(3H, t, J=7.3 Hz).

Example 916-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-(2-methoxyethylthio)purine

6-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-thiopurine (200 mg, 0.687 mmol)and potassium carbonate (190 mg, 1.37 mmol) were dissolved indimethylformamide (10 ml). 2-Methoxyethyl chloride (649 mg, 6.87 mmol)was added thereto and the mixture was stirred at room temperature for 2hours. The reaction mixture was evaporated in vacuo to dryness. Waterwas added to the residue and the solution was extracted with chloroform.The organic layer was dried on magnesium sulfate and evaporated in vacuoto dryness. The residue was purified by silica gel chromatography (2%methanol/chloroform) to give the subject compound (50 mg, yield 21%).

¹H-NMR(DMSO-d₆) δ: 10.12(1H, br s), 7.34(2H, m), 7.15(2H, m), 6.56(2H,br s), 4.87(2H, s), 3.51(2H, t, J=6.8 Hz), 3.24(3H, s), 3.20(2H, t,J=6.8 Hz).

Example 92 Inducing Activity for Biosynthesis of Interferon ExperimentalMethod

1) Animals

C3H/HeJ male mice (5-8 weeks) were purchased from Clea Japan Inc.

2) Reagents

MEM (Osaka University, Microbial Research Center), FCS (GIBCO Co. orFiltron Pty Ltd.), DMSO (Nacalai Tesque Inc.)

3) Test Compounds

About 1 mg of each test compound was accurately weighed and wasdissolved in dimethyl sulfoxide (DMSO) to prepare 1 mM or 10 mM solutionof the test compound. The solution was further diluted 500 times with aculture medium (MEM+10%FCS) and the obtained solution was used as thesample solution in the following tests.

4) Preparation of Spleen Cells and Supernatant of the Cell CultureMedium

After pre-feeding for a week, spleens of 2 or 3 mice were removed. Thespleen was put in PBS(−) solution and a homogenous cell suspension wasprepared by pipetting cells from the spleen. The cell suspension wascentrifuged (1200 rpm, 5 min., 4° C.) to remove the supernatant. Theretowas quickly added 0.2% ice cold NaCl solution (4 ml) under ice coolingto make a suspension. After 30 seconds 1.6% (4 ml) ice-cold NaClsolution was added to the suspension and the mixture was centrifuged toremove the supernatant. The residue was suspended in PBS(−) solution (10ml) and the suspension was centrifuged to remove the supernatant. Theresidue was suspended in 10 ml of the culture medium (MEM+10%FCS) andthe suspension was further centrifuged to remove the supernatant.

Then, the residue was suspended in 5 ml of the culture medium to controlthe viable cell number (2×10⁶ cells/ml by trypan blue-staining). Thusobtained controlled cell suspension was poured into a 24-well plate (0.5ml/well) and the sample solution (0.5 ml) was added to each well (0.5ml/well) and the plate was incubated (37° C., 5% CO₂) for 24 hours.After filtration (0.22 μm) of the supernatant of the culture medium, thefiltrate was kept at −20° C. as a bioassay sample.

5) Quantitative Assay of Interferon α in the Supernatant of the CultureMedium

Immediately after L cells (Dainippon Pharm. Co.) cultured in monolayerculture were treated with trypsin, the cells were added to the culturemedium and the cell suspension (4×10⁵ cell/ml) was prepared bypipetting. Each 100 μl of the cell suspension was poured into all wellsof a 96-well plate (Sumitomo Bakelite Co.) and the plate was incubated(37° C., 5% CO₂) for about 6 hours.

Standard mouse interferon (prepared by Lee Bio Molec. Res Co.) which wasdiluted by serial dilution method with a dilution plate and the abovebioassay sample were poured into an assay plate (each of 50 μl). On theother hand only the culture medium (50 μl) was added to the uninfectedcell control group and to the virus infected cell control group,respectively.

After incubation for 18 hours, the culture medium in the assay plate wasremoved. A solution containing bovine vesicular stomatitis virus [aftercloning virus (3.7×10⁸ PFU/ml) distributed by Domestic Animal ResearchInstitute with BHK cell, the original solution was diluted 300 times]was poured into all of wells (100 μl/well) except the virus uninfectedcontrol group. On the other hand, only the culture medium (100 μl) wasadded to the virus uninfected control group.

After incubation for about 48 hours, the virus solution on the assayplate was removed by suction. A dye solution (neutral red) was pouredinto all wells (50 μl/well). After incubation for 45 minutes, the dyesolution was removed by suction and the wells were washed with PBS(−)solution.

After removal of the PBS(−) solution, UV was irradiated for 10 hours toinactivate the virus. A mixture (100 μl) of 0.1M NaH₂PO₄ and 99.5%ethanol (1:1) was poured into each well and the plate was stirred by amixer for about 5 minutes. After that, the absorption at 540 nm wasmeasured with a plate reader.

6) Result of Measurement

The result was shown in Table 1. The compounds of the present inventionhave inducing activity for biosynthesis of interferon. The drugconcentration in the Table means final concentration.

TABLE 1 INDUCING ACTIVITY FOR BIOSYNTHESIS OF INTERFERON Inducingactivity for biosynthesis of interferon (IU/ml) Example No. (0.1 μM) (1μM) 1 93 46 16 111 26 24 3 34 25 92 50 30 80 19 42 21 13 43 18 17 44 3314 48 28 14 54 47 18 60 31 12 66 40 23 67 36 20 79 7 18 80 25 18 81 2118 82 29 18 88 47 26

Example 93 Activity on Cytokine Production from Mouse Lymph Node CellsExperimental Method

1) Animals

BALB/c female mice were purchased from Japan Charlse River (Yokohama)and female mice (8 weeks) were used.

2) Culture Medium

RPMI1640 medium “DAIGO” (Nippon Seiyaku (Tokyo)) supplemented with 10%heat-inactivated (56° C., 30 min.) Fetal Bovine Serum (characterizedCode No. A-1115-L, HyClone Lab., Logan, Utah) and 50 mM2-mercaptoethanol (Sigma, St. Louis, Mo., Code No. M-6250) were used forthe assay.

3) Test Compounds

Each test compound dissolved in DMSO (Nacalai Tesque (Kyoto) code No.11J) at a concentration of 100 mM was diluted to final concentrationwith the medium.

4) Sensitization and Preparation of Lymph Node Cells

KLM (0.2 mg) was subcutaneously administered to mouse foot with Freund'scomplete adjuvant (Difco Lab., Detroit, Mich., Code No. 3113-60-5). Tendays later popliteal lymph node was picked up and its cell suspensionwas prepared.

5) Production of Cytokine by Stimulation with an Antigen

KLH (0.1 mg/ml) and the drug were added to lymph node cells (5×10⁶cells/ml) and the mixture was incubated at 37° C. under 5% CO₂ for 4days (Corning 25850, 0.15 ml/well). Then amount of cytokine produced inthe supernatant was measured by ELISA specific to cytokine.

Amounts of interleukin 4 (IL-4) and interleukin 5 (IL-5) as a typicalTh2 type cytokine, and interferon γ (IFN-γ) as a typical Th1 typecytokine were measured.

6) Method of Measurement (ELISA)

Amount of IL-4 was measured by ELISA as mentioned below. A ratanti-mouse IL-4 antibody (Pharmingen, San Diego, Calif., Code No.18031D, 0.5 mg/ml) as a primary antibody was diluted 250 times withhydrogen carbonate buffer, and it was seeded to the 96-well plate(Falcon 3912, Becton Dickinson and Company, Franklin Lakes, N.J.) (50ml/well) and each well was coated at 4° C. overnight. Then the plate wasblocked with PBS (−) solution containing 3% BSA (200 ml/well). Afterrinsing and drying the plate, the plate was stored at −20° C. untilbeginning to use. The supernatant of the culture medium was added to thewells (50 ml/well) and the plate was incubated at room temperature for 4hours. Recombinant mouse IL-4 (Pharmingen, Code No. 19231W) was used forpreparing a calibration curve.

After rinsing the plate, a rat anti-mouse IL-4 antibody labeled bybiotin (Pharmingen, Code No. 18042D, 0.5 mg/ml) as a secondary antibody,which was diluted 500 times with PBS (−) solution containing 0.1% BSA,was poured into wells (100 ml/well). The plate was incubated at roomtemperature. The secondary antibody bound to the plate was detected withstreptoabidin alkaliphosphatase (Kirkegaad & Perry Lab., Gaithersburg,Md., Code No. 15-30-00)(0.25 mg/ml, 10 ml/well). After incubation at 37°C. for 1 hour and rinsing of the plate, the coloring was done by addingp-nitrophenyl disodium phosphate substrate (Nacalai Tesque)(1 mg/ml, 100ml/well). The absorption at 415 nm was measured by a microplate reader(MTP-120 Microplatereader, Corona Electric Co.)

Measurement of amounts of IFN-γ was carried out in the same method asmentioned above by using a rat anti-mouse IFN-γ antibody (Pharmingen,San Diego, Calif., Code No. 18181D, 0.5 mg/ml) as a primary antibody anda rat anti-mouse IFN-γ antibody labeled by biotin (Pharmingen, Code No.18112D, 0.5 mg/ml) as a secondary antibody. Recombinant mouse IFN-γ(Pharmingen, Code No. 19301U) was used for preparing a calibrationcurve.

Measurement of amounts of IL-5 was carried out in the same method asmentioned above by using a rat anti-mouse, IL-5 antibody (Pharmingen,San Diego, Calif., Code No. 18051D, 0.5 mg/ml) as a primary antibody anda rat anti-mouse IL-5 antibody labeled by biotin (Pharmingen, Code No.18062D, 0.5 mg/ml) as a secondary antibody. Recombinant mouse IL-5(Pharmingen, Code No. 19241W) was used for preparing a calibrationcurve. The test was carried out three times and their average wascalculated.

The test result on IL-4 was shown in the following Table 2.

TABLE 2 Activity on inhibition for production of IL-4 Example No.Residual amount of IL-4 Inhibition (Concentration of (residual activityDrug 10 μM) (ng/nl) rate %) (%) 1 2.67 31.1 68.9 2 3.81 41.3 58.7 3 1.6311.7 88.3 4 3.81 39.1 60.9 5 5.98 69.1 30.9 7 5.24 53.8 46.2 8 4.98 53.946.1 11 5.84 68.1 21.9 12 3.89 45.4 54.6 15 3.44 40.1 59.9 16 4.75 51.448.6 17 5.25 56.9 43.1 18 6.47 70.1 29.9 19 1.73 12.7 87.3 20 3.38 32.167.9 21 3.86 28.4 71.6 22 2.22 16.3 83.7 23 2.56 18.8 81.2 26 6.64 68.032.0 32 6.78 25.4 74.6 36 5.22 49.6 50.4 42 2.12 7.9 92.1 48 1.89 7.796.3 81 1.50 6.1 93.9 88 2.84 10.7 89.3 89 3.00 28.5 71.5

Example 94 Activity of the Compound on Mouse Contact HypersensitivityReaction Induced by TNCB Test Method

1) Animals

BALB/c female mice (6 weeks old) were purchased from Nippon CharlesRiver Co. (Kanagawa) and they were used after previously feeding for 7days.

2) Sensitization and Induction Method

Hair on mouse abdomen was cut and thereon was spread 7%2,4,6-trinitrochlorobenzen (TNCB) (Tokyo Kasei (Tokyo)) in acetone (0.1ml/mouse) to sensitize (day 0). 6 Days later 1% TNCB in acetone (10 ml)was spread on both sides of left auricula for induction.

3) Administration Method

After dissolving or homogeneously suspending in acetone, a test compound(10 ml) was spread on both sides of left auricula, respectively. Thecompound was applied once one hour before induction. As a positivecontrol an adrenocortical hormone (Betamethasone, Wako Chemical Co.(Osaka)) was used.

4) Method of Measurement of Thickness of Auricula

Right before and 24 hours after spreading hapten (TNCB), thickness ofleft and right auriculae of each mouse was measured under diethyl etheranesthesia by dial thickness gauge (Mitutoyo, Tokyo).

Value of thickness of auricula was calculated by following equation:(Value of thickness of auricula)=(thickness of spread leftauricula)−(thickness of unspread right auricula).

Inhibition rate of thickness was calculated by following equation:

Inhibition rate of thickness={1-[(value of thickness of auricula for 24hours after drug application in drug-applied group)−(value of thicknessof auricula before drug application in drug-applied group)]/[(value ofthickness of auricula 24 hours after acetone application inacetone-applied group)−(value of thickness of auricula before drugapplication in acetone-applied group)]×100.

Result

The result was shown in Table 3.

It was observed that inhibition of thickness of auricula skin 24 hoursafter induction in the group of application of the drug was superior incomparing with the group of application of acetone substrate.

Mouse contact hypersensitivity reaction induced by TNCB is considered asa typical model for human contact dermatitis

Therefore, the result shows that the compounds of the present inventionhave therapeutic and prophylactic activity for human contact dermatitis.

TABLE 3 Dose of Inhibition Standard Example No. drug rate (%) error (%) 1 0.4 mg/ear 79.0 3.7 20 0.4 mg/ear 74.7 8.1 30 0.4 mg/ear 37.3 8.6 320.4 mg/ear 45.1 16.2 42 0.4 mg/ear 59.7 7.5 44 0.4 mg/ear 71.2 2.4 540.4 mg/ear 63.1 1.6 58 0.4 mg/ear 64.4 10.4 60 0.4 mg/ear 85.0 7.6 810.4 mg/ear 79.0 5.2 88 0.4 mg/ear 39.1 10.4 90 0.4 mg/ear 80.3 3.2Betamethasone 0.001 mg/ear 91.0 2.2 Acetone substrate 0.0 9.8

Example 95 Activity of the Compound on Mouse Contact HypersensitivityReaction Induced by TNCB Test Method

The test on compound of Example 79 was carried out in the same method asin Example 94.

Result

The result was shown in Table 4.

It was observed that inhibition of thickness of auricula skin 24 hoursafter induction in the group of application of compound of Example 79was superior in comparing with the group of application of acetonesubstrate.

Mouse contact hypersensitivity reaction induced by the TNCB isconsidered as a typical model for human contact dermatitis

Therefore, the result shows that compound of Example 79 has therapeuticand prophylactic activity for human contact dermatitis.

TABLE 4 Dose of Inhibition Standard Example No. drug rate (%) error (%)79 0.4 mg/ear 68.9 2.3 Betamethasone 0.001 mg/ear 64.4 5.3 Acetonesubstrate 0.0 4.5

Example 96 Activity Against Ear Edema Reaction Induced by ArachidonicAcid Test Method

1) Animal

1) Animals

BALB/c female mice (6 weeks) was purchased from Nippon Charles River Co.(Kanagawa) and they were used after previously feeding until 7 weeksold.

2) Administration Method

After weighing compound of Example 44 it was suspended in acetone (KantoKagaku Co.) (20 mg/ml). The suspension (10 μl) was spread on both sidesof left auricula of mouse under anesthesia with diethyl ether,respectively. As a control acetone (10 μl) was spread on both sides ofleft auricula of another mouse, respectively.

2) Spread of Arachidonic Acid

Two hours after spread of compound of Example 44 or acetone, 10%arachidonic acid (CAYMAN CHEMICAL, Michigan) (10 μl) was spread on bothsides of left auricula, respectively.

3) Measurement of Interdermal Reaction

One hour after spreading 10% arachidonic acid, thickness of both leftand right auriculae was measured under anesthesia with diethyl ether byDial thickness gauge (Mitutoyo, Tokyo).

Value of thickness of the auricula was calculated by following equation:

(Value of thickness of auricula)=(thickness of spread leftauricula)−(thickness of unspread right auricula).

Inhibition rate of the thickness was calculated by following equation:

Inhibition rate of thickness={1−[(value of thickness of auricula 1 hourafter drug application in drug-applied group)−(value of thickness ofauricula before drug application in drug-applied group)]/[(value ofthickness of auricula 1 hour after acetone application inacetone-applied group)−(value of thickness of auricula 1 hour beforeacetone application in acetone-applied group)]×100.

Result

The result was shown in Table 5.

It was observed that inhibition of thickness of auricular skin 1 hourafter induction in the group of application of compound of Example 44was superior in comparing with the group of application of acetonesubstrate.

The result indicates that the compounds of the present invention inhibitdermal inflammatory induced by arachidonic acid.

It is suggested that inflammatory mediators, that is, arachidonic acidmetabolites, such as prostaglandins, leucotrienes andhydroxyeicosatetraenoic acids participate in dermal inflammatory diseasesuch as psoriasis, UV dermatitis, mastocytosis and dermal cancer.

It was suggested that the compounds of the present invention are usefulas therapeutic agents for diseases related to arachidonic acidmetabolites.

TABLE 5 Dose of Inhibition Standard Example No. drug rate (%) error (%)44 0.4 mg/ear 94.03 5.97 Acetone substrate 0.0 25.37

Reference Example 1 6-Amino-2-chloropurine

A solution of 2,6-dichloropurine 0.5 g (2.7 mmol) in 30%ammonia-methanol solution was heated at 100° C. in autoclave for 12hours. The solution was condensed to give the subject compound. Thecompound may be used in next reaction without further purification.

¹H-NMR(DMSO-d₆) δ: 8.13(1H, s), 7.66(2H, br s).

Reference Example 2 6-Amino-9-benzyl-2-chloropurine

6-Amino-2-chloropurine (295 mg) and potassium carbonate (0.55 g, 4.0mmol) were suspended in DMF (10 ml). Benzyl bromide (0.17 ml, 1.4 mmol)was added thereto and the mixture was stirred at room temperature for 4hours. After condensing the suspension in vacuo, to the residue wasadded brine and the mixture was extracted with chloroform. The organiclayer was washed the mixture was with brine, dried on magnesium sulfate,filtered and the solvent in the filtrate was evaporated in vacuo. Theresidue was purified with silica gel chromatography (5%methanol/chloroform) and recrystallized from ethanol to give the subjectcompound (200 mg, yield 58%). m.p. 216-218° C.

UVλ_(max) (EtOH): 265.7 nm; ¹H-NMR(DMSO-d₆) δ: 8.26(1H, s), 7.81(2H, brs), 7.31(5H, m), 5.34(2H, s).

Reference Example 3 6-Amino-9-benzyl-2-methylthiopurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) and sodiummethylthiolate (270 mg, 3.9 mmol) were mixed in DMF (10 ml) and then themixture was stirred at 10° C. for 3.5 hours. To the reaction mixture wasadded brine and the mixture was extracted with ethyl acetate. Theorganic layer was dried on magnesium sulfate, filtered and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (1% methanol/chloroform) to give the subjectcompound (64 mg, yield 61%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.34(5H, m), 5.45(2H,br s), 5.31(2H, s),2.58(3H, s).

Reference Example 4 6-Amino-9-benzyl-2-ethylthiopurine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol,60% in mineral oil) were added ethanethiol (2 ml, 27 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred under heating at 110° C. for 3.5 hours. Brine wasadded thereto and the mixture was extracted with ethyl acetate. Theorganic layer was dried on magnesium sulfate, filtered and the solventin the filtrate was evaporated. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (90mg, yield 82%).

¹H-NMR(CDCl₃) δ: 7.64(1H, s), 7.33(5H, m), 5.91(2H, br s), 5.29(2H, s),3.17(2H, q, J=7.3 Hz), 1.39(3H, t, J=7.3 Hz).

Reference Example 5 6-Amino-9-benzyl-2-propylthiopurine

To DMF suspension (50 ml) containing sodium hydride (917 mg, 23 mmol,60% in mineral oil) were added propanethiol (5.0 ml, 55 mmol) and6-amino-9-benzyl-2-chloropurine (500 mg, 1.9 mmol) in order. The mixturewas stirred under heating at 110° C. for 2.5 hours. Brine was addedthereto and the mixture was extracted with ethyl acetate. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound(505 mg, yield 87%).

¹H-NMR(CDCl₃) δ: 7.64(1H, s), 7.32(5H, m), 6.09(2H, br s), 5.28(2H, s),3.14(2H, t, J=7.3 Hz), 1.76(2H, m), 1.03(3H, t, J=7.3 Hz).

Reference Example 6 6-Amino-9-benzyl-2-(isopropylthio)purine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol60% in mineral oil) were added 2-propanethiol (1.0 ml, 11 mmol) and6-amino-9-benzyl-2-chloropurine (160 mg, 0.62 mmol) in order. Themixture was stirred under heating at 100° C. for 2.5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(112 mg, yield 61%).

¹H-NMR(CDCl₃) δ: 7.64(1H, s), 7.32(5H, m), 5.49(2H, br s), 5.29(2H, s),3.98(1H, m), 1.43(6H, d, J=6.6 Hz).

Reference Example 7 6-Amino-9-benzyl-2-butylthiopurine

6-Amino-9-benzyl-2-chloropurine (310 mg, 1.2 mmol) and sodiumbutylthiolate (670 mg, 6.0 mmol) were mixed in DMF (30 ml) and then themixture was stirred under heating at 100° C. for 4.5 hours. To thereaction mixture was added brine and the mixture was extracted withethyl acetate. The organic layer was dried on magnesium sulfate,filtered and the solvent in the filtrate was evaporated in vacuo. Theresidue was purified with silica gel chromatography (0.5%methanol/chloroform) to give the subject compound (194 mg, yield 52%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.35(5H, m), 5.54(2H, br s), 5.29(2H, s),3.17(2H, t, J=7.3 Hz), 1.72(2H, m), 1.48(2H, m), 0.93(3H, t, J=7.6 Hz).

Reference Example 8 6-Amino-9-benzyl-2-(isobutylthio)purine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol,60% in mineral oil) were added 2-methylpropane-1-thiol (1 ml, 11 mmol)and 6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred under heating at 100° C. for 5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(76 mg, yield 31%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.32(5H, m), 5.46(2H, br s), 5.29(2H, s),3.08(d, 2H, J=6.9 Hz), 2.00(1H, m), 1.04(6H, d, J=6.6 Hz).

Reference Example 9 6-Amino-9-benzyl-2-(sec-butylthio)purine

To DMF suspension (10 ml) containing sodium hydrate (300 mg, 7.5 mmol,60%in mineral oil) were added 2-butanethiol (1 ml, 11 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred under heating at 100° C. for 5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(85 mg, yield 35%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.32(5H, m), 5.46(2H, br s), 5.29(2H, s),3.85(1H, m), 1.75(2H, m), 1.42(3H, d, J=6.9 Hz), 1.03(3H, t, J=7.6 Hz).

Reference Example 10 6-Amino-9-benzyl-2-pentylthiopurine

To DMF suspension (10 ml) containing sodium hydride (277 mg, 6.9 mmol,60% in mineral oil) were added 1-pentanethiol (2 ml, 16 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred under heating at 110° C. for 4 hours. Brine wasadded thereto and the mixture was extracted with ethyl acetate. Theorganic layer was dried on magnesium sulfate, filtered and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (1% methanol/chloroform) to give the subjectcompound (102 mg, yield 81%).

¹H-NMR(CDCl₃) δ: 7.64(1H, s), 7.33(5H, m), 5.77(2H, br s), 5.29(2H, s),3.16(2H, t, J=7.3 Hz), 1.75(2H, m), 1.33-1.46(4H, m), 0.89(3H, t, J=7.3Hz).

Reference Example 11 6-Amino-9-benzyl-2-(3-methylbutyl)thiopurine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol,60% in mineral oil) were added 3-methylbutane-1-thiol (1 ml, 8.0 mmol)and 6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred under heating at 100° C. for 2.5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(120 mg, yield 48%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.32(5H, m), 5.44(2H, br s), 5.29(2H, s),3.17(2H, t, J=7.9 Hz), 1.64(3H, m), 0.94(6H, d, J=6.6 Hz).

Reference Example 12 6-Amino-9-benzyl-2-(2-methylbutyl)thiopurine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol,60% in mineral oil) were added 2-methylbutane-1-thiol (1 ml, 8.0 mmol)and 6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred under heating at 100° C. for 4.5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtered and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(80 mg, yield 32%).

¹H-NMR(CDCl₃) δ: 7.63(1H, s), 7.32(5H, m), 5.50(2H, br s), 5.30(2H, s),3.26(1H, q, J=5.9 Hz), 2.99(1H, q, J=7.6 Hz), 1.78(1H, m), 1.55(1H, m),1.28(1H, m), 1.02(3H, d, J=11.9 Hz), 0.92(3H, t, J=11.8 Hz).

Reference Example 13 6-Amino-9-benzyl-2-cyclohexylthiopurine

To DMF suspension (10 ml) containing sodium hydride (256 mg, 6.4 mmol,60% in mineral oil) were added cyclohexanethiol (2 ml, 16 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was heated at 100° C. for 3.5 hours. Brine was added thereto andthe mixture was extracted with ethyl acetate. The organic layer wasdried on magnesium sulfate, filtrated and the solvent in the filtratewas evaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound(112 mg, yield 86%).

¹H-NMR(CDCl₃) δ: 7.65(1H, s), 7.33(5H, m), 5.86(2H, br s), 5.28(2H, m),3.75-3.87(1H, m), 2.11-2.17(2H, m), 1.25-1.67(8H, m).

Reference Example 14 6-Amino-9-benzyl-2-phenylthiopurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and sodiumthiophenolate (2 g, 15 mmol) were mixed in DMF (12 ml) and then themixture was stirred under heating at 100° C. for 7.5 hours. To thereaction mixture was added brine and the mixture was extracted withethyl acetate. The organic layer was dried on magnesium sulfate,filtered and the solvent in the filtrate was evaporated in vacuo. Theresidue was purified with silica gel chromatography (0.5%methanol/chloroform) to give the subject compound (228 mg, yield 89%).

¹H-NMR(CDCl₃) δ: 7.65-7.70(3H, m), 7.41-7.45(3H, m), 7.28-7.33(3H, m),7.15-7.20(2H, m), 5.54(2H, br s), 5.09(2H, s).

Reference Example 15 6-Amino-9-benzyl-2-(p-tolylthio)purine

To DMF suspension (10 ml) containing sodium hydride (300 mg, 7.5 mmol,60% in mineral oil) were added p-toluenethiol (1.9 g, 15 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred under heating at 100° C. for 3 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtrated and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(124 mg, yield 93%).

¹H-NMR(CDCl₃) δ: 7.62(1H, s), 7.55(2H, d, J=8.2 Hz), 7.15-7.31(7H, m),5.61(2H, br s), 5.10(2H, s), 2.40(3H, s).

Reference Example 16 6-Amino-9-benzyl-2-(2-naphthylthio)purine

To DMF suspension (20 ml) containing sodium hydride (800 mg, 20 mmol,60% in mineral oil) were added 2-naphthalenethiol (3.8 g, 24 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred under heating at 100° C. for 10.5 hours. Brine wasadded thereto and the mixture was extracted with chloroform. The organiclayer was dried on magnesium sulfate, filtrated and the solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (0.5% methanol/chloroform) to give the subjectcompound (244 mg, yield 83%).

¹H-NMR(CDCl₃) δ: 8.17(1H, s), 7.52-7.92(7H, m), 7.06-7.30(5H, m),5.63(2H, br s), 5.04(2H, s).

Reference Example 17 6-Amino-9-benzyl-2-benzylthiopurine

To DMF suspension (10 ml) containing sodium hydride (410 mg, 10 mmol,60% in mineral oil) were added α-toluenethiol (1.7 ml, 14 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred under heating at 100° C. for 4.5 hours. Brine wasadded thereto and the mixture was extracted with ethyl acetate. Theorganic layer was dried on magnesium sulfate, filtrated and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (0.5% methanol/chloroform) to give the subjectcompound (97 mg, yield 73%).

¹H-NMR(CDCl₃) δ: 7.64(1H, s), 7.22-7.45(10H, m), 5.48(2H, br s),5.31(2H, s), 4.43(2H, s).

Reference Example 18 6-Amino-9-benzyl-8-bromo-2-methylthiopurine

6-Amino-9-benzyl-2-methylthiopurine (100 mg, 0.37 mmol) and bromine (0.5ml) were dissolved in 100 ml of methylene chloride and the solution wasstirred at room temperature for 3 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onmagnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (0.5% methanol/chloroform) to give the subject compound(10 mg, yield 8%).

¹H-NMR(CDCl₃) δ: 7.34(5H, m), 5.64(2H, br s), 5.33(2H, s), 2.57(3H, s).

Reference Example 19 6-Amino-9-benzyl-8-bromo-2-ethylthiopurine

6-Amino-9-benzyl-2-ethylthiopurine (214 mg, 0.75 mmol) and bromine (0.5ml) were dissolved in 100 ml of methylene chloride and the solution wasstirred at room temperature for 7 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onmagnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (43mg, yield 16%).

¹H-NMR(CDCl₃) δ: 7.32(5H, m), 5.82(2H, br s), 5.32(2H, s), 3.16(2H, q,J=7.3 Hz), 1.39(3H, t, J=7.3 Hz).

Reference Example 20 6-Amino-9-benzyl-8-bromo-2-propylthiopurine

6-Amino-9-benzyl-2-propylthiopurine (290 mg, 0.97 mmol) and bromine (0.7ml) were dissolved in 160 ml of methylene chloride and the solution wasstirred at room temperature for 4.5 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (58mg, yield 16%).

¹H-NMR(CDCl₃) δ: 7.35(5H, m), 5.70(2H, br s), 5.32(2H, s), 3.13(2H, t,J=7.6 Hz), 1.76(2H, m), 1.04(3H, t, J=7.6 Hz).

Reference Example 21 6-Amino-9-benzyl-8-bromo-2-(isopropylthio)purine

6-Amino-9-benzyl-2-(isopropylthio)purine (60 mg, 0.20 mmol) and bromine(0.4 ml) were dissolved in 85 ml of methylene chloride and the solutionwas stirred at room temperature for 2 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (20mg, yield 26%).

¹H-NMR(CDCl₃) δ: 7.34(5H, m), 5.72(2H, br s), 5.32(2H, s), 3.96(1H, m),1.42(6H, d, J=7.0 Hz).

Reference Example 22 6-Amino-9-benzyl-8-bromo-2-butylthiopurine

6-Amino-9-benzyl-2-butylthiopurine (163 mg, 0.52 mmol) and bromine (0.6ml) were dissolved in 180 ml of methylene chloride and the solution wasstirred at room temperature for 4.5 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (35mg, yield 17%).

¹H-NMR(CDCl₃) δ: 7.34(5H, m), 5.81(2H, br s), 5.32(2H, s), 3.15(2H, t,J=7.3 Hz), 1.72(2H, m), 1.45(2H, m), 0.92(3H, t, J=7.6 Hz).

Reference Example 23 6-Amino-9-benzyl-8-bromo-2-(isobutylthio)purine

6-Amino-9-benzyl-2-(isobutylthio)purine (60 mg, 0.19 mmol) and bromine(0.4 ml) were dissolved in 85 ml of methylene chloride and the solutionwas stirred at room temperature for 2 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (chloroform) to give the subject compound (20 mg, yield27%).

¹H-NMR(CDCl₃) δ: 7.34(5H, m), 5.59(2H, br s), 5.32(2H, s), 3.07(2H, t,J=6.6 Hz), 1.96(1H, m), 1.04(6H, d, J=6.6 Hz).

Reference Example 24 6-Amino-9-benzyl-8-bromo-2-(sec-butylthio)purine

6-Amino-9-benzyl-2-(sec-butylthio)purine (60 mg, 0.19 inmol) and bromine(0.4 ml) were dissolved in 85 ml of methylene chloride and the solutionwas stirred at room temperature for 2 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (chloroform) to give the subject compound (53 mg, yield71%).

¹H-NMR(CDCl₃) δ: 7.34(5H, m), 5.45(2H, br s), 5.32(2H, s), 3.83(1H, m),1.63(2H, m), 1.42(3H, d, J=7.0 Hz), 1.03(3H, t, J=7.3 Hz).

Reference Example 25 6-Amino-9-benzyl-8-bromo-2-pentylthiopurine

6-Amino-9-benzyl-2-pentylthiopurine (260 mg, 0.79 mmol) and bromine (0.5ml) were dissolved in 100 ml of methylene chloride and the solution wasstirred at room temperature for 7 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onmagnesium sulfate and filtered. The solvent of the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (49mg, yield 15%).

¹H-NMR(CDCl₃) δ: 7.33(5H, m), 5.95(2H, br s), 5.31(2H, s), 3.14(2H, t,J=7.3 Hz), 1.74(2H, m), 1.27-1.47(4H, m), 0.88(3H, t, J=7.3 Hz).

Reference Example 266-Amino-9-benzyl-8-bromo-2-(3-methylbutyl)thiopurine

6-Amino-9-benzyl-2-(3-methylbutyl)thiopurine (260 mg, 0.79 mmol) andbromine (0.5 ml) were dissolved in 100 ml of methylene chloride and thesolution was stirred at room temperature for 7 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on magnesium sulfate and filtered. The solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(49 mg, yield 15%).

¹H-NMR(CDCl₃) δ: 7.33(5H, m), 5.52(2H, br s), 5.30(2H, s), 3.15(2H, t,J=7.9 Hz), 1.61-1.76(3H, m), 0.92(6H, t, J=6.2 Hz).

Reference Example 276-Amino-9-benzyl-8-bromo-2-(2-methylbutyl)thiopurine

6-Amino-9-benzyl-2-(2-methylbutyl)thiopurine (60 mg, 0.18 mmol) andbromine (0.4 ml) were dissolved in 90 ml of methylene chloride and thesolution was stirred at room temperature for 7 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on magnesium sulfate and filtered. The solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(39 mg, yield 53%).

¹H-NMR(CDCl₃) δ: 7.33(5H, m), 5.44(2H, br s), 5.32(2H, s), 3.24(1H, q,J=7.9 Hz), 2.98(1H, q, J=7.3 Hz), 1.75(1H, m), 1.52(1H, m), 1.28(1H, m),1.01(3H, d, J=6.6 Hz), 0.91(3H, t, J=7.3 Hz).

Reference Example 28 6-Amino-9-benzyl-8-bromo-2-cyclohaxylthiopurine

6-Amino-9-benzyl-2-cyclohexylthiopurine (178 mg, 0.52 mmol) and bromine(0.4 ml) were dissolved in 90 ml of methylene chloride and the solutionwas stirred at room temperature for 7 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (0.5% methanol/chloroform) to give the subject compound(86 mg, yield 40%).

¹H-NMR(CDCl₃) δ: 7.30-7.45(5H, m), 5.69(2H, br s), 5.31(2H, s), 3.80(1H,m), 2.10(2H, m), 1.25-1.78(8H, m).

Reference Example 29 6-Amino-9-benzyl-8-bromo-2-phenylthiopurine

6-Amino-9-benzyl-2-phenylthiopurine (95 mg, 0.28 mmol) and bromine (0.4ml) were dissolved in 150 ml of methylene chloride and the solution wasstirred at room temperature for 4.5 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtered wasevaporated in vacuo. The residue was purified with silica gelchromatography (0.5% methanol/chloroform) to give the subject compound(25 mg, yield 22%).

¹H-NMR(CDCl₃) δ: 7.65-7.68(2H, m), 7.42-7.44(3H, m), 7.20-7.28(5H, m),5.49(2H, br s), 5.09(2H, s).

Reference Example 30 6-Amino-9-benzyl-8-bromo-2-(p-tolylthio)purine

6-Amino-9-benzyl-2-(p-tolylthio)purine (86 mg, 0.37 mmol) and bromine(0.4 ml) were dissolved in 120 ml of methylene chloride and the solutionwas stirred at room temperature for 4 hours. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on magnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (0.5% methanol/chloroform) to give the subject compound(20 mg, yield 19%).

¹H-NMR(CDCl₃) δ: 7.55(2H, d, J=7.9 Hz), 7.20-7.28(7H, m), 5.40(2H, brs), 5.10(2H, s), 2.41(3H, s).

Reference Example 31 6-Amino-9-benzyl-8-bromo-2-(2-naphthylthio)purine

6-Amino-9-benzyl-2-(2-naphthylthio)purine (221 mg, 0.58 mmol) andbromine (0.4 ml) were dissolved in 160 ml of methylene chloride and thesolution was stirred at room temperature for 5.5 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on magnesium sulfate and filtered. The solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (0.5% methanol/chloroform) to give the subjectcompound (118 mg, yield 44%).

¹H-NMR(CDCl₃) δ: 8.42(1H, d, J=8.3 Hz), 7.80-7.87(3H, m), 7.52-7.66(2H,m), 7.04-7.21(6H, m), 5.56(2H, br s), 5.00(2H, s).

Reference Example 32 6-Amino-9-benzyl-2-benzylthio-8-bromopurine

6-Amino-9-benzyl-2-benzylthiopurine (176 mg, 0.51 mmol) and bromine (1ml) were dissolved in 160 ml of methylene chloride and the solution wasstirred at room temperature for 4 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onmagnesium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (0.5% methanol/chloroform) to give the subject compound(19 mg, yield 9%).

¹H-NMR(CDCl₃) δ: 7.21-7.39(10H, m), 5.50(2H, br s), 5.33(2H, s),4.41(2H, m).

Reference Example 33 6-Amino-9-benzyl-2-methoxypurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and sodium methylate(208 mg, 3.85 mmol) were dissolved in methanol (20 ml) and then thesolution was refluxed on heating under stirring for 30 hours. Thereaction mixture was evaporated in vacuo to dryness. To the residue wasadded water and the mixture was extracted with chloroform. The organiclayer was dried on sodium sulfate and evaporated in vacuo to dryness.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (151 mg, yield 77%).

¹H-NMR(DMSO-d₆) δ: 8.05(1H, s), 7.37-7.25(7H, m), 5.26(2H, s), 3.81(3H,s).

Reference Example 34 6-Amino-9-benzyl-2-ethoxypurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and sodium ethylate(262 mg, 3.85 mmol) were dissolved in ethanol (20 ml) and then thesolution was refluxed on heating under stirring for 20 hours. Thereaction mixture was evaporated in vacuo to dryness. To the residue wasadded water and the mixture was extracted with chloroform. The organiclayer was dried on sodium sulfate and evaporated in vacuo to dryness.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (151 mg, yield 73%).

¹H-NMR(DMSO-d₆) δ: 8.04(1H, s), 7.37-7.21(7H, m), 5.25(2H, s), 4.25(2H,q, J=7.1 Hz), 1.27(3H, t, J=7.1 Hz).

Reference Example 35 6-Amino-9-benzyl-2-propoxypurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and sodium propylate(316 mg, 3.85 mmol) were dissolved in 1-propanol (20 ml) and then thesolution was refluxed on heating under stirring for 3 hours. Thereaction mixture was evaporated in vacuo to dryness. To the residue wasadded water and the mixture was extracted with chloroform. The organiclayer was dried on sodium sulfate and evaporated in vacuo to dryness.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (162 mg, yield 74%).

¹H-NMR(DMSO-d₆) δ: 8.04(1H, s), 7.37-7.21(7H, m), 5.26(2H, s), 4.16(2H,t, J=6.6 Hz), 1.68(2H, m), 0.95(3H, t, J=7.3 Hz).

Reference Example 36 6-Amino-9-benzyl-2-butoxypurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and sodium butylate(370 mg, 3.85 mmol) were dissolved in 1-butanol (20 ml) and then thesolution was refluxed on heating under stirring for 2 hours. Thereaction mixture was evaporated in vacuo to dryness. To the residue wasadded water and the mixture was extracted with chloroform. The organiclayer was dried on sodium sulfate and evaporated in vacuo to dryness.The residue was purified with silica gel chromatography (2%methanol/chloroform) to of give the subject compound (131 mg, yield54%).

¹H-NMR(DMSO-d₆) δ: 8.03(1H, s), 7.37-7.21(7H, m), 5.25(2H, s), 4.20(2H,t, J=6.4 Hz), 1.65(2H, m), 1.39(2H, m), 0.92(3H, t, J=7.3 Hz).

Reference Example 37 6-Amino-9-benzyl-2-pentoxypurine

6-Amino-9-benzyl-2-chloropurine (150 mg, 0.58 mmol) and sodium pentylate(318 mg, 2.89 mmol) were dissolved in 1-pentanol (50 ml) and then thesolution was stirred under heating at 130° C. for 5 hours. The reactionmixture was evaporated in vacuo to dryness. To the residue was addedwater and the mixture was extracted with chloroform. The organic layerwas dried on sodium sulfate and evaporated in vacuo to dryness. Theresidue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (103 mg, yield 57%).

¹H-NMR(DMSO-d₆) δ: 8.03(1H, s), 7.37-7.25(5H, m), 7.20(2H, br s),5.26(2H, s), 4.20(2H, t, J=6.6 Hz), 1.67(2H, m), 1.33(4H, m), 0.88(3H,t, J=6.6 Hz).

Reference Example 38 6-Amino-9-benzyl-8-bromo-2-methoxypurine

6-Amino-9-benzyl-2-methoxypurine (118 mg, 0.46 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 5 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and evaporated in vacuo to dryness. The residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (90 mg, yield 58%).

¹H-NMR(DMSO-d₆) δ: 7.48 (2H, br s), 7.39-7.24 (5H, m), 5.26 (2H, s),3.82 (3H, s).

Reference Example 39 6-Amino-9-benzyl-8-bromo-2-ethoxypurine

6-Amino-9-benzyl-2-ethoxypurine (143 mg, 0.53 mmol) and bromine (0.5 ml)were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 5 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated and driedon sodium sulfate, filtered and evaporated in vacuo to dryness. Theresidue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (42 mg, yield 23%).

¹H-NMR(DMSO-d₆) δ: 7.43(2H, br s), 7.38-7.24(5H, m), 5.25(2H, s),4.26(2H, q, J=7.1 Hz), 1.28(3H, t, J=7.1 Hz).

Reference Example 40 6-Amino-9-benzyl-8-bromo-2-propoxypurine

6-Amino-9-benzyl-2-ethoxypurine (134 mg, 0.473 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 5 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated and driedon sodium sulfate and evaporated in vacuo to dryness. The residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (55 mg, yield 32%).

¹H-NMR(DMSO-d₆) δ: 7.43(2H, br s), 7.38-7.23(5H, m), 5.25(2H, s),4.16(2H, t, J=6.6 Hz), 1.70(2H, m), 0.94(3H, t, J=7.3 Hz).

Reference Example 41 6-Amino-9-benzyl-8-bromo-2-butoxypurine

6-Amino-9-benzyl-2-butoxypurine (120 mg, 0.404 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 5 hours. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated and driedon sodium sulfate and evaporated in vacuo to dryness. The residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (97 mg, yield 64%).

¹H-NMR(DMSO-d₆) δ: 7.44(2H, br s), 7.37-7.23(5H, m), 5.26(2H, s),4.21(2H, t, J=6.4 Hz), 1.64(2H, m), 1.39(2H, m), 0.91(3H, t, J=7.3 Hz).

Reference Example 42 6-Amino-9-benzyl-8-bromo-2-pentoxypurine

6-Amino-9-benzyl-2-pentoxypurine (95 mg, 0.305 mmol) and bromine (0.5ml) were dissolved in 100 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated and driedon sodium sulfate and evaporated in vacuo to dryness. The residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (78 mg, yield 82%).

¹H-NMR(DMSO-d₆) δ: 7.42(2H, br s), 7.37-7.22(5H, m), 5.25(2H, s),4.19(2H, t, J=6.4 Hz), 1.66(2H, m), 1.33(4H, m), 0.88(3H, t, J=6.8 Hz).

Reference Example 43 2,6-Diamino-9-benzylpurine

2,6-Diaminopurine (5.00 g, 33.3 mmol) and potassium carbonate (6.91 g,50.0 mmol) were suspended in DMF (250 ml). Benzyl bromide (8.55 g, 50mmol) was added thereto and the mixture was stirred at room temperaturefor 5 hours. After condensing the reaction mixture in vacuo, to theresidue was added water and the mixture was extracted with chloroform.The organic layer was dried on sodium sulfate, filtered and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (5% methanol/chloroform) to give the subjectcompound (1.56 g, yield 19%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.36-7.21 (5H, m), 6.69 (2H, br s),5.80 (2H, br s), 5.19 (2H, s).

Reference Example 44 6-Amino-9-benzyl-2-methylaminopurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and 40%methylamine/methanol solution (50 ml) were heated at 120° C. for 20hours in autoclave. The reaction mixture was condensed in vacuo. To theresidue was added 5N aqueous sodium hydroxide and the solution wasextracted with chloroform. The organic layer was dried on sodiumsulfate, filtered and the solvent in the filtrate was evaporated invacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (163 mg, yield 83%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.36-7.26 (5H, m), 6.68 (2H, br s),6.20 (1H, q, J=4.8 Hz), 5.19 (2H, s), 2.76 (3H, d, J=4.8 Hz).

Reference Example 45 6-Amino-9-benzyl-2-ethylaminopurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and aqueousethylamine (50 ml) were heated at 120° C. for 20 hours in autoclave. Thereaction mixture was condensed in vacuo. To the residue was added 5Naqueous sodium hydroxide and the mixture was extracted with chloroform.The organic layer was dried on sodium sulfate, filtered and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (2% methanol/chloroform) to give the subjectcompound (147 mg, yield 71%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.36-7.26 (5H, m), 6.65 (2H, br s),6.22 (1H, t, J=5.7 Hz), 5.18 (2H, s), 3.26 (2H, m), 1.09 (3H, t, J=7.1Hz).

Reference Example 46 6-Amino-9-benzyl-2-propylaminopurine

6-Amino-9-benzyl-2-chloropurine (10 mg, 0.385 mmol) and propylamine (228mg, 3.85 mmol) in methanol (50 ml) were heated at 120° C. for 10 hoursin autoclave. The reaction mixture was condensed in vacuo and to theresidue was added 5N aqueous sodium hydroxide, followed by extractionwith chloroform. The organic layer was dried on sodium sulfate, filteredand the solvent in the filtrate was evaporated in vacuo. The residue waspurified with silica gel chromatography (2% methanol/chloroform) to givethe subject compound (99 mg, yield 91%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.33-7.26 (5H, m), 6.64 (2H, br s),6.25 (1H, t, J=5.7 Hz), 5.17 (2H, s), 3.18 (2H, m), 1.50 (2H, m), 0.87(3H, t, J=7.5 Hz).

Reference Example 47 6-Amino-9-benzyl-2-butylamtnopurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.38S5 mmol) and butylamine(282 mg, 3.85 mmol) in methanol (50 ml) were heated at 120° C. for 10hours in autoclave. The reaction mixture was condensed in vacuo. To theresidue was added 5N aqueous sodium hydroxide and the solution wasextracted with chloroform. The organic layer was dried on sodiumsulfate, filtered and the solvent in the filtrate was evaporated invacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (113 mg, yield 99%).

¹H-NMR(DMSO-d₆) δ: 7.82 (1H, s), 7.34-7.26 (5H, m), 6.81 (2H, br s),6.34 (1H, t, J=6.2 Hz), 5.18 (2H, s), 3.24 (2H, m), 1.49 (2H, m), 1.31(2H, m), 0.88 (3H, t, J=7.3 Hz).

Reference Example 48 6-Amino-9-benzyl-2-pentylaminopurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and pentylamine(336 mg, 3.85 mmol) suspended in 1-butanol (10 ml) were heated at 100°C. for 10 hours in autoclave. The reaction mixture was condensed invacuo. To the residue was added 1N aqueous sodium hydroxide and thesolution was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (83 mg, yield 70%).

¹H-NMR(DMSO-d₆) δ: 7.79 (1H, s), 7.32-7.26 (5H, m), 6.62 (2H, br s),6.21 (1H, t, J=6.0 Hz), 5.17 (2H, s), 3.25-3.18 (2H,m), 1.52-1.47 (2H,m), 1.30-1.26 (4H, m), 0.86 (3H, t, J=6.6 Hz).

Reference Example 49 6-Amino-9-benzyl-2-(isopropylamino)puring

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and isopropylamine(228 mg, 3.85 mmol) suspended in 1-butanol (10 ml) were heated at 100°C. for 10 hours in autoclave. The reaction mixture was condensed invacuo. To the residue was added 1N aqueous sodium hydroxide and thesolution was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (89 mg, yield 82%).

¹H-NMR(DMSO-d₆) δ: 7.79 (1H, s), 7.36-7.26 (5H, m), 6.62 (2H, br s),6.00 (1H, d, J=8.9 Hz), 5.17 (2H, s), 4.10-3.98 (1H, m), 1.11 (6H, d,J=6.6 Hz).

Reference Example 50 6-Amino-9-benzyl-2-(isobutylamino)purine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and isobutylamine(288 mg, 3.85 mmol) suspended in 1-butanol (10 ml) were heated at 100°C. for 10 hours in autoclave. The reaction mixture was condensed invacuo. To the residue was added 1N aqueous sodium hydroxide and thesolution was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (89 mg, yield 78%).

¹H-NMR(DMSO-d₆) δ: 7.79 (1H, s), 7.33-7.26 (5H, m), 6.62 (2H, br s),6.28 (1H, t, J=6.0 Hz), 5.17 (2H, s), 3.07 (2H, dd, J=6.0, 6.0 Hz),1.89-1.79 (1H, m), 0.87 (6H, d, J=6.8 Hz).

Reference Example 51 6-Amino-9-benzyl-2-(sec-butylamino)purine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and sec-butylamine(282 mg, 3.85 mmol) suspended in 1-butanol (10 ml) were heated at 100°C. for 10 hours in autoclave. The reaction mixture was condensed invacuo. To the residue was added 1N aqueous sodium hydroxide and themixture was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (71 mg, yield 62.8%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.33-7.26 (5H, m), 6.60 (2H, br s),5.97 (1H, d, J=8.4 Hz), 5.17 (2H, s), 3.90-3.85 (1H, m), 1.54-1.38 (2H,m), 1.08 (3H, d, J=6.4 Hz), 0.85 (3H, t, J=7.3 Hz).

Reference Example 52 6-Amino-9-benzyl-2-(2,2-dimethylpropyl)aminopurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and neo-pentylamine(336 mg, 3.85 mmol) suspended in 1-butanol (10 ml) were heated at 100°C. for 10 hours in autoclave. The reaction mixture was condensed invacuo. To the residue was added 1N aqueous sodium hydroxide and thesolution was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (88 mg, yield 74%).

¹H-NMR(DMSO-d₆) δ: 7.78 (1H, s), 7.32-7.24 (5H, m), 6.61 (2H, br s),6.08 (1H, t, J=6.2 Hz), 5.17 (2H, s), 3.15 (2H, d, J=6.2 Hz), 0.87 (9H,s).

Reference Example 53 6-Amino-9-benzyl-2-benzylaminopurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and benzylamine (825mg, 7.70 mmol) in 1-butanol (10 ml) were refluxed on heating for 8hours. The reaction mixture was condensed in vacuo. To the residue wasadded 5N aqueous sodium hydroxide and the solution was extracted withchloroform. The organic layer was dried on sodium sulfate, filtered andthe solvent in the filtrate was evaporated in vacuo. The residue waspurified with silica gel chromatography (2% methanol/chloroform) to givethe subject compound (171 mg, yield 67%).

¹H-NMR(DMSO-d₆) δ: 7.80 (1H, s), 7.34-7.15 (10H, m), 6.86 (1H, t, J=6.4Hz), 6.69 (2H, br s), 5.15 (2H, s), 4.47 (2H, d, J=6.4 Hz).

Reference Example 54 6-Amino-9-benzyl-2-cyclohexylaminopurine

6-Amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) and cyclohexylamine(764 mg, 7.70 mmol) in 1-butanol (10 ml) were refluxed on heating for 60hours. The reaction mixture was condensed in vacuo. To the residue wasadded 5N aqueous sodium hydroxide and the solution was extracted withchloroform. The organic layer was dried on sodium sulfate, filtered andthe solvent in the filtrate was evaporated in vacuo. The residue waspurified with silica gel chromatography (2% methanol/chloroform) to givethe subject compound (115 mg, yield 46%).

¹H-NMR(DMSO-d₆) δ: 7.79 (1H, s), 7.33-7.26 (5H, m), 6.60 (2H, br s),6.00 (1H, d, J=8.1 Hz), 5.16 (2H, s), 3.71 (1H, m), 1.86 (2H, m), 1.72(2H, m), 1.68 (1H, m), 1.31-1.14 (5H, m).

Reference Example 55 6-Amino-2-anilino-9-benzylpurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and aniline (359mg, 3.85 mmol) in 1-butanol (10 ml) were refluxed on heating for 20hours. The reaction mixture was condensed in vacuo. To the residue wasadded 5N aqueous sodium hydroxide and the mixture was extracted withchloroform. The organic layer was dried on sodium sulfate, filtered andthe solvent in the filtrate was evaporated in vacuo. The residue waspurified with silica gel chromatography (2% methanol/chloroform) to givethe subject compound (108 mg, yield 89%).

¹H-NMR(DMSO-d₆) δ: 8.88 (1H, s), 7.98 (1H, s), 7.81 (2H, d, J=7.9 Hz),7.38-7.25 (5H, m), 7.20 (2H, t, J=8.3 Hz), 6.95 (2H, br s), 6.83 (1H, t,J=7.3 Hz), 5.29 (2H, s).

Reference Example 56 6-Amino-9-benzyl-2-dimethylaminopurine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) and aqueousdimethylamine (30 ml) were heated at 120° C. for 15 hours in autoclave.The reaction mixture was condensed in vacuo. To the residue was added 5Naqueous sodium hydroxide and the solution was extracted with chloroform.The organic layer was dried on sodium sulfate, filtered and the solventin the filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (2% methanol/chloroform) to give the subjectcompound (90 mg, yield 87%).

¹H-NMR(DMSO-d₆) δ: 7.82 (1H, s), 7.37-7.25 (5H, m), 6.73 (2H, br s),5.19 (2H, s), 3.07 (6H, s).

Reference Example 57 6-Amino-9-benzyl-(N-benzylmethylamino)purine

6-Amino-9-benzyl-2-chloropurine (100 mg, 0.385 mmol) andN-methylbenzylamine (467 mg, 3.85 mmol) in 1-butanol (30 ml) wererefluxed on heating for 10 hours. The reaction mixture was condensed invacuo. To the residue was added 5N aqueous sodium hydroxide and themixture was extracted with chloroform. The organic layer was dried onsodium sulfate, filtered and the solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (97 mg, yield 73%).

¹H-NMR(DMSO-d₆) δ: 7.85 (1H, s), 7.35-7.19 (10H, m), 6.78 (2H, br s),5.18 (2H, s), 4.85 (2H, s), 3.05 (3H, s).

Reference Example 58 2,6-Diamino-9-benzyl-8-bromopurine

2,6-Diamino-9-benzylpurine (1.00 g, 4.16 mmol) and bromine (1 ml) weredissolved in 100 ml of methylene chloride and the solution was stirredat room temperature for 5 hours. Aqueous sodium thiosulfate was added tothe reaction mixture. The organic layer was separated, dried on sodiumsulfate and filtered. The solvent in the filtrate was evaporated invacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (0.62 g, yield 47%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.16 (5H, m), 6.92 (2H, br s), 5.99 (2H, br s),5.18 (2H, s).

Reference Example 59 6-Amino-9-benzyl-8-bromo-2-methylaminopurine

6-Amino-9-benzyl-2-methylaminopurine (75 mg, 0.30 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and filtered. The solvent of the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (73 mg, yield 74%).

¹H-NMR(DMSO-d₆) δ: 7.38-7.22 (5H, m), 6.90 (2H, br s), 6.39 (1H, q,J=4.8 Hz), 5.18 (2H, s), 2.75 (3H, d, J=4.8 Hz).

Reference Example 60 6-Amino-9-benzyl-8-bromo-2-ethylaminopurine

6-Amino-9-benzyl-2-ethylaminopurine (75 mg, 0.28 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and filtered. The solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (63 mg, yield 65%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.23 (5H, m), 6.87 (2H, br s), 6.41 (1H, t,J=5.5 Hz), 5.17 (2H, s), 3.25 (2H, m), 1.08 (3H, t, J=7.1 Hz).

Reference Example 61 6-Amino-9-benzyl-8-bromo-2-propylaminopurine

6-Amino-9-benzyl-2-propylaminopurine (87 mg, 0.31 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and filtered. The solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (95 mg, yield 85%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.23 (5H, m), 6.85 (2H, br s), 6.44 (1H, t,J=5.7 Hz), 5.17 (2H, s), 3.18 (2H, m), 1.50 (2H, m), 0.86 (3H, t, J=7.3Hz).

Reference Example 62 6-Amino-9-benzyl-8-bromo-2-butylaminopurine

6-Amino-9-benzyl-2-butylaminopurine (101 mg, 0.34 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and filtered. The solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (116 mg, yield 91%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.26 (5H, m), 6.85 (2H, br s), 6.42 (1H, t,J=6.2 Hz), 5.17 (2H, s), 3.22 (2H, m), 1.46 (2H, m), 1.30 (2H, m), 0.87(3H, t, J=7.3 Hz).

Reference Example 63 6-Amino-9-benzyl-8-bromo-2-pentylaminopurine

6-Amino-9-benzyl-2-pentylaminopurine (70 mg, 0.23 mmol) and bromine (0.5ml) were dissolved in 50 ml of methylene chloride and the solution wasstirred at room temperature for 1 hour. Aqueous sodium thiosulfate wasadded to the reaction mixture. The organic layer was separated, dried onsodium sulfate and filtered. The solvent in the filtrate was evaporatedin vacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (80 mg, yield 91%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.24 (5H, m), 6.84 (2H, br s), 6.41 (1H, t,J=5.7 Hz), 5.17 (2H, s), 3.25-3.18 (2H,m), 1.52-1.47 (2H, m), 1.29-1.24(4H, m), 0.85 (3H, t, J=6.9 Hz).

Reference Example 64 6-Amino-9-benzyl-8-bromo-2-(isopropylamino)purine

6-Amino-9-benzyl-2-(isopropylamino)purine (71 mg, 0.25 mmol) and bromine(0.5 ml) were dissolved in 50 ml of methylene chloride and the solutionwas stirred at room temperature for 1 hour. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on sodium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (73mg, yield 81%).

¹H-NMR(DMSO-d₆) δ: 7.38-7.23 (5H, m), 6.84 (2H, br s), 6.21 (1H, d,J=8.1 Hz), 5.17 (2H, s), 4.09-3.99 (1H, m), 1.11 (6H, d, J=6.4 Hz).

Reference Example 65 6-Amino-9-benzyl-8-bromo-2-(isobutylamino)purine

6-Amino-9-benzyl-2-(isobutylamino)purine (75 mg, 0.25 mmol) and bromine(0.5 ml) were dissolved in 50 ml of methylene chloride and the solutionwas stirred at room temperature for 1 hour. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on sodium sulfate and filtered. The solvent of the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (62mg, yield 65%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.27 (5H, m), 6.83 (2H, br s), 6.47 (1H, t,J=6.0 Hz), 5.17 (2H, s), 3.06 (2H, dd, J=6.0, 6.0 Hz), 1.88-1.78 (1H,m), 0.86 (6H, d, J=6.8 Hz).

Reference Example 66 6-Amino-9-benzyl-8-bromo-2-(sec-butylamino)purine

6-Amino-9-benzyl-2-(sec-butylamino)purine (58 mg, 0.20 mmol) and bromine(0.5 ml) were dissolved in 50 ml of methylene chloride and the solutionwas stirred at room temperature for 1 hour. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on sodium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (57mg, yield 78%).

¹H-NMR(DMSO-d₆) δ: 7.35-7.25 (5H, m), 6.80 (2H, br s), 6.16 (1H, d,J=8.6 Hz), 5.15 (2H, s), 3.88-3.81 (1H, m), 1.50-1.36 (2H, m), 1.05 (3H,d, J=6.4 Hz), 0.83 (3H, t, J=7.3 Hz).

Reference Example 676-Amino-9-benzyl-8-bromo-2-(2,2-dimethylpropyl)aminopurine

6-Amino-9-benzyl-2-(2,2-dimethyipropyl)aminopurine (69 mg, 0.22 mmol)and bromine (0.5 ml) were dissolved in 50 ml of methylene chloride andthe solution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and filtered. The solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(75 mg, yield 87%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.23 (5H, m), 6.82 (2H, br s), 6.29 (1H, t,J=6.2 Hz), 5.18 (2H, s), 3.14 (2H, d, J=6.2 Hz), 0.86 (9H, s).

Reference Example 68 6-Amino-9-benzyl-2-(N-benzylamino)-8-bromopurine

6-Amino-9-benzyl-2-(N-benzylamino)purine (60 mg, 0.18 mmol) and bromine(0.5 ml) were dissolved in 50 ml of methylene chloride and the solutionwas stirred at room temperature for 1 hour. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on sodium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (37mg, yield 50%).

¹H-NMR(DMSO-d₆) δ: 7.33-7.20 (10H, m), 7.05 (1H, t, J=6.4 Hz), 6.91 (2H,br s), 5.15 (2H, s), 4.46 (2H, d, J=6.4 Hz).

Reference Example 69 6-Amino-9-benzyl-8-bromo-2-cyclohexylaminopurine

6-Amino-9-benzyl-2-cyclohexylaminopurine (100 mg, 0.31 mmol) and bromine(0.5 ml) were dissolved in 50 ml of methylene chloride and the solutionwas stirred at room temperature for 1 hour. Aqueous sodium thiosulfatewas added to the reaction mixture. The organic layer was separated,dried on sodium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound(105 mg, yield 84%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.27 (5H, m), 6.81 (2H, br s), 6.20 (1H, d,J=7.9 Hz), 5.16 (2H, s), 3.68 (1H, m), 1.87 (2H, m), 1.69 (2H, m), 1.58(1H, m), 1.30-1.12 (5H, m).

Reference Example 70 6-Amino-2-anilino-9-benzyl-8-bromopurine

6-Amino-2-anilino-9-benzylpurine (87 mg, 0.31 mmol) was dissolved in amixture of methylene chloride (50 ml) and acetic acid (10 ml). To thesolution were added sodium acetate (105 mg, 1.28 mmol) and bromine (0.5ml), and the mixture was stirred at room temperature for 3 hour. Aqueoussodium thiosulfate was added to the reaction mixture. The organic layerwas separated, washed with aqueous saturated sodium hydrogen carbonate,dried on sodium sulfate and filtered. The solvent in the filtrate wasevaporated in vacuo. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (93mg, yield 92%).

¹H-NMR(DMSO-d₆) δ: 8.30 (1H, d, J=8.8 Hz), 7.82 (1H, d, J=2.4 Hz), 7.71(1H, s), 7.49 (1H, dd, J=9.0, 2.4 Hz), 7.39-7.25 (9H, m), 5.27 (2H, s).

Reference Example 71 6-Amino-9-benzyl-8-bromo-2-dimethylaminopurine

6-Amino-9-benzyl-2-dimethylaminopurine (66 mg, 0.25 mmol) was dissolvedin a mixture of methylene chloride (50 ml) and acetic acid (10 ml). Tothe solution were added sodium acetate (202 mg, 2.46 mmol) and bromine(0.5 ml), and the mixture was stirred at room temperature for 1 hour.Aqueous sodium thiosulfate was added to the reaction mixture. Theorganic layer was separated, washed with aqueous saturated sodiumhydrogen carbonate, dried on sodium sulfate and filtered. The solvent inthe filtrate was evaporated in vacuo. The residue was purified withsilica gel chromatography (1% methanol/chloroform) to give the subjectcompound (68 mg, yield 80%).

¹H-NMR(DMSO-d₆) δ: 7.38-7.25 (5H, m), 6.95 (2H, br s), 5.19 (2H, s),3.07 (6H, s).

Reference Example 726-Amino-9-benzyl-2-(N-benzylmethylamino)-8-bromopurine

6-Amino-9-benzyl-2-(N-benzylmethylamino)purine (77 mg, 0.22 mmol) andbromine (0.5 ml) were dissolved in 50 ml of methylene chloride and thesolution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and filtered. The solvent in thefiltrate was evaporated in vacuo. The residue was purified with silicagel chromatography (1% methanol/chloroform) to give the subject compound(91 mg, yield 96%).

¹H-NMR(DMSO-d₆) δ: 7.31-7.19 (10H, m), 7.00 (2H, br s), 5.18 (2H, s),4.84 (2H, s), 3.05 (3H, s).

Reference Example 73 5-Amino-1-benzyl-4-cyano-2-hydroxyimidazole

Benzylisocyanate (25 g, 188 mmol) and N,N-diisopropylethylamine (23.5ml, 130 mmol) were added to aminomalononitrile p-toluenesulfonate (45 g,178 mmol) suspended in tetrahydrofuran. The mixture was stirred at roomtemperature for 14 hours and then the solvent was removed in vacuo. Tothe residue was added ethyl acetate and the solution was washed and theorganic layer was dried on magnesium sulfate. The solvent was removed invacuo. To the residue was added tetrahydrofuran and 1N aqueous sodiumhydroxide. The solution was stirred at 50° C. for 20 minutes, andneutralized with 15% aqueous potassium hydrogen sulfide. The resultingcrystals were filtered and dried to give the subject compound (41 g,106%). The crude product was used for next reaction without furtherpurification.

¹H NMR (δ, DMSO-d₆): 9.91 (s, 1H), 7.31 (m, 5H), 6.51(br s, 2H), 4.76(s, 2H).

Reference Example 74 1-Amino-9-benzyl-8-hydroxy-2-mercaptpurine

Crude 5-amino-1-benzyl-4-cyano-2-hydroxyimidazole (31.3 g, 146 mmol) ofReference Example 73 was suspended in tetrahydrofuran and to thesuspension was dropped benzoylisothiocyanate (41 ml, 305 mmol). Afterstirring overnight, the solvent was removed in vacuo and to the residuewas added ether. The crystals were filtered and dissolved in a mixtureof tetrahydrofuran and 2N aqueous sodium hydroxide. The solution wasrefluxed for 50 hours and then, neutralized with 10% aqueous potassiumhydrogen sulfide. The resulting crystals were filtered to give a mixture(27.8 g) of the subject compound and6-amino-7-benzyl-8-hydroxy-2-mercaptpurine. The mixture wasrecrystallized from ethyl acetate to give only the subject compound.

¹H NMR (δ, DMSO-d₆): 12.10 (br s, 1H), 10.06 (br s, 1H), 7.36-7.24 (m,5H), 6.74 (br s, 2H), 4.85 (s, 2H).

Reference Example 75 6-Amino-9-benzyl-2,8-dimethoxypurine

To 6-amino-9-benzyl-8-bromo-2-methoxypurine (125 mg, 0.374 mmol) in 10ml of methanol was added 10N aqueous sodium hydroxide (50 ml) and thesolution was refluxed under heating for 2 hours. The reaction mixturewas concentrated in vacuo to dryness and to the residue was added water.The mixture was extracted with chloroform and the organic layer wasdried on sodium sulfate. After removal of the solvent the residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (83 mg, yield 78%).

¹H-NMR(DMSO-d₆) δ: 7.73-7.23(5H, m), 6.90(2H, br s), 5.05(2H, s),4.04(3H, s), 3.78(3H, s).

Reference Example 76 6-Amino-9-benzyl-2-ethoxy-8-methoxypurine

To 6-amino-9-benzyl-8-bromo-2-ethoxypurine (35 mg, 0.101 mmol) in 5 mlof methanol was added 10N aqueous sodium hydroxide (50 ml) and thesolution was refluxed under heating for 2 hours. The reaction mixturewas concentrated in vacuo to dryness and to the residue was added water.The mixture was extracted with chloroform and the organic layer wasdried on sodium sulfate. After removal of the solvent the residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (22 mg, yield 73%).

¹H-NMR(DMSO-d₆) δ: 7.73-7.23(5H, m), 6.86(2H, br s), 5.04(2H, s),4.22(2H, q, J=7.1 Hz), 4.04(3H, s), 1.27(3H, t, J=7.1 Hz).

Reference Example 77 6-Amino-9-benzyl-8-methoxy-2-propoxypurine

To 6-amino-9-benzyl-8-bromo-2-propoxypurine (123 mg, 0.339 mmol) in 10ml of methanol was added 10N aqueous sodium hydroxide (50 ml) and thesolution was refluxed under heating for 2 hours. The reaction mixturewas concentrated in vacuo to dryness and to the residue was added water.The mixture was extracted with chloroform and the organic layer wasdried on sodium sulfate. After removal of the solvent the residue waspurified with silica gel chromatography (1% methanol/chloroform) to givethe subject compound (99 mg, yield 93%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.22(5H, m), 6.86(2H, br s), 5.04(2H, s),4.12(2H, t, J=6.8 Hz), 4.04(3H, s), 1.67(2H, m), 0.94(3H, t, J=7.3 Hz).

Reference Example 78 6-Amino-9-benzyl-2-(2-methoxyethyl)aminopurine

6-Amino-9-benzyl-2-chloropurine (10 mg, 0.385 mmol) and2-methoxyethylamine in 2 ml of butanol were heated at 120° C. for 9hours in autoclave. The reaction mixture was concentrated in vacuo todryness and to the residue was added water. The mixture was extractedwith chloroform and the organic layer was dried on sodium sulfate andconcentrated in vacuo to dryness. The residue was purified with silicagel chromatography (3% methanol/chloroform) to give the subject compound(83 mg, yield 72%).

¹H-NMR(DMSO-d₆) δ: 7.81(1H, s), 7.35-7.26(5H, m), 6.72(2H, br s),6.18(1H, t, J=4.8 Hz), 5.19(2H, s), 3.45-3.36(4H, m), 3.24(3H, s).

Reference Example 796-Amino-9-benzyl-8-bromo-2-(2-methoxyethylamino)purine

6-Amino-9-benzyl-2-(2-methoxyethyl)aminopurine (70 mg, 0.24 mmol) andbromine (0.5 ml) were dissolved in methylene chloride (50 ml). Thesolution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and concentrated in vacuo to dryness.The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (71 mg, yield 80%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.23(5H, m), 6.94(2H, br s), 6.38(1H, t, J=4.8Hz), 5.18(2H, s), 3.45-3.36(4H, m), 3.23(3H, s).

Reference Example 806-Amino-9-benzyl-8-methoxy-2-(2-methoxyethyl]aminopurine

6-Amino-9-benzyl-8-bromo-2-(2-methoxyethyl)aminopurine (68 mg, 0.18mmol) was dissolved in 28% sodium methoxide in methanol (30 ml) and thesolution was refluxed on heating under stirring for 4 hours. Thereaction mixture was concentrated in vacuo to dryness and to the residuewas added water. The mixture was extracted with chloroform and theorganic layer was dried on sodium sulfate and concentrated in vacuo todryness. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (26 mg, yield 44%).

¹H-NMR(DMSO-d₆) δ: 7.35-7.21(5H, m), 6.36(2H, br s), 6.01 (1H, t, J=4.8Hz), 4.98(2H, s), 3.99(3H, s), 3.45-3.36(4H, m), 3.23 (3H, S).

Reference Example 81 6-Amino-9-benzyl-8-methoxy-2-(2-ethoxyethoxy)purine

6-Amino-9-benzyl-2-chloropurine (500 mg, 1.93 mmol) was dissolved in 40ml of sodium 2-ethoxyethoxy in 2-ethoxyethanol and the solution washeated at 100° C. for 6 hours. The reaction mixture was concentrated invacuo to dryness and to the residue was added water. The mixture wasextracted with chloroform and the organic layer was washed with water,dried on sodium sulfate and concentrated in vacuo to dryness. Theresidue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (410 mg, yield 68%).

¹H-NMR(DMSO-d₆) δ: 8.05(1H, s), 7.38-7.26(5H, m), 7.24(2H, br s),5.26(2H, s), 4.32(2H, t, J=4.8 Hz), 3.65(2H, t, J=4.8 Hz), 3.47(2H, q,J=7.0 Hz), 1.11(3H, t, J=7.0 Hz).

Reference Example 82 6-Amino-9-benzyl-8-bromo-2-(2-ethoxyethoxy)purine

6-Amino-9-benzyl-2-(2-ethoxyethoxy)purine (300 mg, 0.96 mmol) andbromine (2.0 ml) were dissolved in methylene chloride (50 ml). Thesolution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and concentrated in vacuo to dryness.The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (256 mg, yield 68%).

¹H-NMR(DMSO-d₆) δ: 7.47(2H, br s), 7.39-7.23(5H, m), 5.26(2H, s),4.32(2H, t, J=4.8 Hz), 3.65(2H,t, J=4.8 Hz), 3.47(2H, q, J=7.0 Hz),1.11(3H, t, J=7.0 Hz).

Reference Example 83 6-Amino-9-benzyl-2-(2-ethoxyethoxyl-8-methoxypurine

6-Amino-9-benzyl-8-bromo-2-(2-ethoxyethoxy)purine (206 mg, 0.18 mmol)was dissolved in 1N sodium hydroxide in methanol (20 ml) and the mixturewas refluxed on heating under stirring for 2 hours. The reaction mixturewas concentrated in vacuo to dryness, and to the residue was addedwater. The solution was extracted with chloroform and the organic layerwas dried on sodium sulfate and concentrated in vacuo to dryness. Theresidue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (123 mg, yield 68%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.23(5H, m), 6.89(2H, br s), 5.04(2H, s),4.29(2H, t, J=4.6 Hz), 4.05(3H, s), 3.64(2H, t, J=4.6 Hz), 3.47(2H, q,J=7.0 Hz), 1.11(3H, t, J=7.0 Hz).

Reference Example 84 6-Amino-2-chloro-9-(4-fluorobenzyl)purine

6-Amino-2-chloropurine (5.02 g) and potassium carbonate (5 g, 36 mmol)were suspended in DMF (200 ml) and thereto was added 4-fluorobenzylchloride (5 ml, 42 mmol). The mixture was stirred at room temperaturefor 3 hours. The reaction mixture was concentrated in vacuo to dryness,and to the residue was added water. The mixture was extracted withchloroform and the organic layer was washed with water, dried on sodiumsulfate and concentrated in vacuo to dryness. The residue was purifiedwith silica gel chromatography (2% methanol/chloroform) to give thesubject compound (162 g).

¹H-NMR(DMSO-dE) δ: 8.25(1H, s), 7.80(2H, br s), 7.37(5H, m), 7.18(2H,m), 5.33(2H, s).

Reference Example 856-Amino-9-(4-fluorobenzyl)-2-(2-methoxyethoxy)purine

6-Amino-9-(4-fluorobenzyl)purine (100 mg, 0.36 mmol) was dissolved in 30ml of sodium 2-mehoxyethoxide in 2-methoxyethanol and the solution washeated at 20° C. for 3 hours. The reaction mixture was concentrated invacuo to dryness and to the residue was added water. The mixture wasextracted with chloroform and the organic layer was washed with water,dried on sodium sulfate and concentrated in vacuo to dryness. Theresidue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (109 mg, yield 95%).

¹H-NMR(DMSO-d₆) δ: 8.05(1H, s), 7.40 (2H, m), 7.24(2H, br s), 7.17(2H,m), 5.25(2H, s), 4.33(2H, t, J=4.4 Hz), 3.62(2H, t, J=4.4 Hz), 3.29(3H,s).

Reference Example 866-Amino-8-bromo-9-(fluorobenzyl)-2-(2-methoxyethoxy)purine

6-Amino-9-(4-fluorobenzyl)-2-(2-methoxyethoxy)purine (mg, 0.96 mmol) andbromine (1.0 ml) were dissolved in methylene chloride (20 ml). Thesolution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and concentrated in vacuo to dryness.The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (79 mg, yield 69%).

¹H-NMR(DMSO-d₆) δ: 7.46(2H, br s), 7.31(2H, m), 7.19(2H, m), 5.24(2H,s), 4.34(2H, t, J=4.6 Hz), 3.62(2H,t, J=4.6 Hz), 3.29(3H, s).

Reference Example 876-Amino-9-(4-fuluorobenzyl)-8-methoxy-2-(2-methoxyethoxy)purine

6-Amino-8-bromo-9-(4-fluorobenzyl)-2-(2-methoxyethoxy)purine (70 mg,0.18 mmol) was dissolved in 1N sodium hydroxide in methanol (20 ml) andthe solution was refluxed on heating under stirring for 2 hours. Thereaction mixture was concentrated in vacuo to dryness, and to theresidue was added water. The mixture was extracted with chloroform andthe organic layer was dried on sodium sulfate and concentrated in vacuoto dryness. The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (57 mg, yield 93%).

¹H-NMR(DMSO-d₆) δ: 7.31(2H, m), 7.16(2H, m), 6.87(2H, br s), 5.02(2H,s), 4.30(2H, t, J=4.6 Hz), 4.05(3H, s), 3.61(2H, t, J=4.6 Hz), 3.29(3H,s).

Reference Example 885-Amino-4-cyano-1-(4-fluorobenzyl)-2-hydroxyimidazole

4-Fluorobenzylisocyanate (1.37 g, 10 mmol) and N,N-diisopropylethylamine(1.29 g, 10 mmol) were added to aminomalononitrile p-toluenesulfonate(2.53 g, 10 mmol) suspended in tetrahydrofuran (50 ml). The mixture wasstirred at room temperature for 24 hours and then the solvent wasremoved in vacuo. To the residue was added ethyl acetate and thesolution was washed and the organic layer was extracted with 1N aqueoussodium hydroxide. The extract was neutralized with 10% aqueous potassiumhydrogen sulfide and extracted with ethyl acetate. The organic layer wasdried on sodium sulfate and the solvent was removed in vacuo. Theresidue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (1.93 g, yield 89%).

¹H-NMR (DMSO-d₆): 9.93(1H, br s), 7.31(2H, m), 7.15(2H, m), 6.53(2H, brs), 4.75(2H, s).

Reference Example 89 6-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-thiopurine

5-amino-4-cyano-1-(4-fluorobenzyl)-2-hydroxyimidazole (1.90 g, 8.79mmol) was suspended in tetrahydrofuran (50 ml) and to the suspension wasdropped benzoylisothiocyanate (2.87 g, 17.6 mmol). After stirring atroom temperature for 8 hours, the solvent was removed in vacuo and tothe residue was added ether. The crystals were filtered and refluxed ina mixture of tetrahydrofuran and 1N aqueous sodium hydroxide for 40hours and neutralized with 10% aqueous potassium hydrogen sulfide. Thecrystals were harvested by filtration to give the subject compound (1.22g, yield: 48%).

¹H NMR (δ, DMSO-d₆): 10.14(1H, s), 7.31(2H, m), 7.15(2H, m), 6.83(2H,s), 4.84(2H, s).

Reference Example 90 6-Amino-9-benzyl-2,8-dihydroxypurine

6-Amino-9-benzyl-8-bromo-2-methoxypurine (75 mg, 0.224 mmol) inconcentrated hydrochloric acid (15 ml) was refluxed under heating for 5hours. The reaction mixture was made basic by 28% aqueous ammonia, thecrystals were filtered, washed with water and purified by silica gelchromatography (0.2%aqueous ammonia-5% methanol/chroloform) to give thesubject compound (12 mg, yield 21%).

¹H-NMR(DMSO-d₆) δ: 9.64(2H, br s), 7.34-7.22(6H, m), 6.51(2H, br s),4.78(2H, s).

Reference Example 91 2,6-Diamino-9-benzyl-8-purinol

2,6-Diamino-9-benzyl-8-bromopurine (400 mg, 1.25 mmol) in concentratedhydrochloric acid (20 ml) was refluxed under heating for 5 hours. Thereaction mixture was made basic by 28% aqueous ammonia, the crystalswere filtered, washed with water and dried to give the subject compound(138 mg, yield 43%).

¹H-NMR(DMSO-d₆) δ: 9.63 (1H, br s), 7.34-7.22 (5H, m), 6.02 (2H, br s),5.74 (2H, br s), 4.81 (2H, s).

Reference Example 92 6-Amino-9-benzyl-2-(2-aminoethyl)thiopurine

To sodium hydride (300 mg, 7.5 mmol, 60% in mineral oil) were added DMF(10 ml), 2-aminoethanethiol (620 mg, 8 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred at 100° C. for 3 hours. After addition of saturatedbrine the reaction mixture was extracted with chloroform and the organiclayer was dried on magnesium sulfate and concentrated in vacuo todryness. The residue was purified with silica gel chromatography (10%methanol/chloroform) to give the subject compound (126 mg, yield 54%).

¹H NMR (CDCl₃) δ: 7.64 (s, 1H), 7.31-7.26 (m, 5H), 5.53 (br s, 2H), 5.29(s, 2H), 3.26 (t, 2H, J=6.0 Hz), 3.02 (t, 2H, J=6.3 Hz).

Reference Example 93 6-Amino-9-benzyl-2-(2-dimethylaminoethyl)thiopurine

To sodium hydride (600 mg, 15 mmol 60% in mineral oil) were added DMF(10 ml), 2-dimethylaminoethanethiol (1.3 g, 9.2 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred at 100° C. for 10 hours. After addition of saturatedbrine the reaction mixture was extracted with chloroform and the organiclayer was dried on magnesium sulfate and concentrated in vacuo todryness. The residue was purified with silica gel chromatography (10%methanol/chloroform) to give the subject compound (24 mg, yield 21%).

¹H NMR (CDCl₃) δ: 7.63 (s, 1H), 7.36-7.26 (m, 5H), 5.55 (br s, 2H), 5.30(s, 2H), 3.29 (t, 2H, J=7.6 Hz), 2.68 (t, 2H, J=7.9 Hz), 2.30 (s, 6H),1.80 (br s, 2H).

Reference Example 94 3-(6-Amino-9-benzyl-2-purinyl)thiopropionic Acid

To sodium hydride (300 mg, 7.5 mmol 60% in mineral oil) were added DMF(10 ml), 3-mercaptopropionic acid (1 ml, 11 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred at 100° C. for 5 hours. After addition of saturatedbrine, the reaction mixture was acidified with 2N hydrochloric acid andextracted with chloroform. The organic layer was dried on magnesiumsulfate and concentrated in vacuo to dryness. The residue was purifiedwith silica gel chromatography (4% methanol/chloroform) to give thesubject compound (120 mg, yield 47%).

¹H NMR (DMSO-d₆) δ: 12.26 (br s, 1H); 8.16 (s, 1H), 7.39-7.17 (m, 5H),5.29 (s, 2H), 3.22 (t, 2H, J=7.2 Hz), 2.66 (t, 2H, J=6.9 Hz).

Reference Example 95 2-(2-Acetylaminoethyl)thio-6-amino-9-benzylpurine

To 6-amino-9-benzyl-2-(2-aminoethyl)thiopurine (50 mg, 0.17 mmol)suspended in 2 ml of dichloromethane was added triethylamine (30 ml, 0.2mmol) and then acetic acid anhydride (20 ml, 0.2 mmol) under icecooling. After 1 hour the mixture warmed to room temperature. Theretowas added saturated brine. The mixture was extracted with chloroform andthe organic layer was dried on magnesium sulfate and concentrated invacuo to dryness. The residue was purified with silica gelchromatography (1% methanol/chloroform) to give the subject compound (34mg, yield 66%).

¹H NMR (CDCl₃) δ: 7.67 (s, 1H), 7.34-7.26 (m, 5H), 6.17 (br s, 3H), 5.31(s, 2H), 3.59 (q, 2H, J=5.6 Hz), 3.31 (t, 2H, J=5.2 Hz).

Reference Example 96 Methyl-3-(6-amino-9-benzyl-2-purinyl)thiopropionate

To 3-(6-amino-9-benzyl-2-purinyl) thiopropionic acid (100 mg, 0.30 mmol)suspended in 10 ml of chloroform was added thionylchloride (0.14 ml, 2mmol). After refluxing under heating for 1 hour methanol was dropped tothe mixture under ice cooling. The solvent was removed in vacuo and theresidue was purified by silica gel chromatography (1%methanol/chloroform) to give the subject compound (70 mg, yield 68%).

¹H NMR (CDCl₃) δ: 7.65 (s, 1H), 7.36-7.26 (m, 5H), 5.67 (br s, 2H), 5.28(s, 2H), 3.69 (s, 3H), 3.39 (t, 2H, J=7.3 Hz), 2.82 (t, 2H, J=7.6 Hz).

Reference Example 97 N-Methyl-(6-amino-9-benzyl-2-purinyl)thioacetamide

Sodium hydride (320 mg, 8 mmol 60% in mineral oil) was washed withhexane. Thereto were added DMF (10 ml), 2-mercapto-N-methylacetamide (1ml) and 6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order.The mixture was stirred at 100° C. for 8 hours. After addition ofsaturated brine the reaction mixture was extracted with ethyl acetate.The organic layer was dried on magnesium sulfate and the solvent wasremoved in vacuo. The residue was purified with silica gelchromatography (3% methanol/chloroform) to give the subject compound(158 mg, yield 60%).

¹H NMR (DMSO-d₆) δ: 8.14 (s, 1H), 7.87 (br s, 1H), 7.33 (m, 5H), 5.30(s, 2H), 3.75 (s, 2H), 2.53 (d, 3H, J=4.6 Hz).

Reference Example 98 3-(6-Amino-9-benzyl-2-purinyl)thio-1-propanol

Sodium hydride (600 mg, 15 mmol 60% in mineral oil) were added DMF (10ml), 3-mercapto-1-propanol (1 ml, 12 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred at 100° C. for 2 hours. After addition of saturatedbrine the reaction mixture was extracted with ethyl acetate. The organiclayer was dried on magnesium sulfate and the solvent was removed invacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (30 mg, yield 12%).

¹H NMR (CDCl₃) δ: 7.62 (s, 1H), 7.37-7.26 (m, 5H), 5.59 (br s, 2H), 5.29(s, 2H), 3.76 (m, 3H), 3.33 (t, 2H, J=6.3 Hz), 1.96 (m, 2H).

Reference Example 99 3-(6-Amino-9-benzyl-2-purinylithio-1-propanethiol

Sodium hydride (600 mg, 15 mmol 60% in mineral oil) were added DMF (10ml), 1,3-propanedithiol (1 ml, 10 mmol) and6-amino-9-benzyl-2-chloropurine (200 mg, 0.77 mmol) in order. Themixture was stirred at 100° C. for 2 hours. After addition of saturatedbrine the reaction mixture was extracted with ethyl acetate. The organiclayer was dried on magnesium sulfate and the solvent was removed invacuo. The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (135 mg, yield 53%).

¹H NMR (CDCl₃) δ: 7.65 (s, 1H), 7.36-7.26 (m, 5H), 5.56 (br s, 2H), 5.31(s, 2H), 3.28 (t, 2H, J=6.6 Hz), 2.65 (m, 2H), 2.05 (m, 2H), 1.40 (t,1H, J=7.9 Hz).

Reference Example 100 6-Amino-9-benzyl-2-(2-phenylethyl)thiopurine

Sodium hydride (300 mg, 7.5 mmol 60% in mineral oil) were added DMF (10ml), 2-phenylethanethiol (1 ml, 7 mmol) and6-amino-9-benzyl-2-chloropurine (100 mg, 0.39 mmol) in order. Themixture was stirred at 100° C. for 10 hours. After addition of saturatedbrine the mixture was extracted with ethyl acetate. The organic layerwas dried on magnesium sulfate and the solvent was removed in vacuo. Theresidue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (51 mg, yield 37%).

¹H NMR (CDCl₃) δ: 7.65 (s, 1H), 7.32-7.24 (m, 5H), 5.57 (br s, 2H), 5.33(s, 2H), 3.39 (dd, 2H, J=10.6, 7.6 Hz), 3.07 (dd, 2H, J=15.8, 7.2 Hz).

Reference Example 101 6-Amino-9-benzyl-2-(2-hydroxyethoxy)purine

To sodium (74 mg, 3.2 mmol) in 5 ml of ethylene glycol were added6-amino-9-benzyl-2-chloropurine (157 mg, 0.58 mmol). The mixture washeated at 100° C. for 4 hours and concentrated in vacuo to dryness. Tothe residue was added water and the mixture was extracted withchloroform. The organic layer was dried on magnesium sulfate and thesolvent was removed in vacuo. The residue was purified with silica gelchromatography (3% methanol/chloroform) to give the subject compound(121 mg, yield 70%).

¹H-NMR(DMSO-d₆) δ: 8.04(1H, s), 7.32(5H, m), 7.22(2H, br s), 5.25(2H,s), 4.81(1H, t, J=5.3 Hz), 4.22(2H, t, J=4.9 Hz), 3.68(2H, q, J=5.3 Hz).

Reference Example 102 6-Amino-9-benzyl-8-bromo-2-(2-hydroxyethoxy)purine

6-Amino-9-benzyl-2-(2-methoxyethoxy)purine (100 mg, 0.36 mmol) andbromine (0.25 ml) were dissolved in methylene chloride (100 ml). Thesolution was stirred at room temperature for 6 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and the solvent was removed in vacuo.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (55 mg, yield 43%).

¹H-NMR(DMSO-d₆) δ: 7.44(2H, br s), 7.36-7.23(5H, m), 5.25(2H, s),4.82(1H, t, J=5.6 Hz), 4.22(2H, t, J=5.0 Hz), 3.66(2H, q, J=5.0 Hz).

Reference Example 1036-Amino-9-benzyl-2-(2-hydroxyethoxyl)-8-methoxypurine

6-Amino-9-benzyl-8-bromo-2-(2-methoxyethoxyl)purine (130 mg, 0.36 mmol)in methanol (50 ml) was dissolved in 28% sodium methoxide/methanol (3ml) and the solution was refluxed on heating under stirring for 10hours. The reaction mixture was concentrated in vacuo to dryness, and tothe residue was added saturated brine. The mixture was extracted withchloroform and the organic layer was dried on sodium sulfate, followedby removal of the solvent. The residue was purified with silica gelchromatography (3% methanol/chloroform) to give the subject compound (78mg, yield 69%).

¹H-NMR(DMSO-d₆) δ: 7.26(5H, m), 6.86(2H, br s), 5.03(2H, s), 4.78(1H, t,J=5.6 Hz), 4.18(2H, t, J=5.0 Hz), 4.04(3H, s), 3.66(2H, m).

Reference Example 104 6-Amino-9-benzyl-2-(3-hydroxypropoxy)purine

Sodium (80 mg, 3.5 mmol) in 3 ml of 1,3-propanediol was added6-amino-9-benzyl-2-chloropurine (235 mg, 0.90 mmol). The mixture washeated at 100° C. for 3 hours. The reaction mixture was concentrated invacuo to dryness. To the residue was added water and the mixture wasextracted with chloroform. The organic layer was dried on sodium sulfateand the solvent was removed. The residue was purified with silica gelchromatography (3% methanol/chloroform) to give the subject compound(137 mg, yield 51%).

¹H-NMR(DMSO-d₆) δ: 8.03(1H, s), 7.32(5H, m), 7.21(2H, br s), 5.25(2H,s), 4.51(1H, t, J=4.9 Hz), 4.26(2H, t, J=6.3 Hz), 3.52(2H, q, J=5.6 Hz),1.81(2H, m).

Reference Example 1056-Amino-9-benzyl-8-bromo-2-(3-hydroxypropoxy)purine

6-Amino-9-benzyl-2-(3-hydroxypropoxy)purine (210 mg, 0.7 mmol) andbromine (0.5 ml) were dissolved in methylene chloride (200 ml). Thesolution was stirred at room temperature for 4 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on magnesium sulfate and concentrated in vacuo todryness. The residue was purified with silica gel chromatography (5%methanol/chloroform) to give the subject compound (143 mg, yield 54%).

¹H-NMR(DMSO-d₆) δ: 7.45(2H, br s), 7.32(5H, m), 5.25(2H, s), 4.52(1H, t,J=5.0 Hz), 4.26(2H, t, J=6.6 Hz), 3.52(2H, q, J=5.6 Hz), 1.81(2H, m).

Reference Example 1066-Amino-9-benzyl-2-(3-hydroxypropoxy)-8-methoxypurine

6-Amino-9-benzyl-8-bromo-2-(3-hydroxypropoxy)purine (140 mg, 0.37 mmol)in methanol (50 ml) was dissolved in 28%. sodium methoxide/methanol (3ml) and the solution was refluxed on heating under stirring for 10hours. The reaction mixture was concentrated in vacuo to dryness and tothe residue was added saturated brine. The mixture was extracted withchloroform and the organic layer was dried on sodium sulfate and thesolvent was removed. The residue was purified with silica gelchromatography (3% methanol/chloroform) to give the subject compound (88mg, yield 72%).

¹H-NMR(DMSO-d₆) δ: 7.31(5H, m), 6.86(2H, br s), 5.04(2H, s), 4.50(1H, t,J=5.0 Hz), 4.22(2H, t, J=6.6 Hz), 4.03(3H, s), 3.52(2H, m), 1.80(2H, m).

Reference Example 107 6-Amino-9-benzyl-2-(3-ethoxypropoxy)purine

To sodium (150 mg, 6.5 mmol) in 5 ml of 3-ethoxypropanol were added6-amino-9-benzyl-2-chloropurine (500 mg, 1.93 mmol) and DMF (10 ml). Themixture was heated at 120° C. for 1 hour. The reaction mixture wasconcentrated in vacuo to dryness. To the residue was added water and themixture was extracted with chloroform. The organic layer was dried onsodium sulfate and the solvent was removed. The residue was purifiedwith silica gel chromatography (2% methanol/chloroform) to give thesubject compound (481 mg, yield 76%).

¹H-NMR(DMSO-d₆) δ: 8.04(1H, s), 7.34-7.25(5H, m), 7.24(2H, br s),5.27(2H, s), 4.27(2H, t, J=6.4 Hz), 3.48(2H, t, J=6.4 Hz), 3.41(2H, q,J=7.0 Hz), 1.91(2H, m), 1.10(3H, t, J=7.0 Hz).

Reference Example 108 6-Amino-9-benzyl-8-bromo-2-(3-ethoxypropoxy)purine

6-Amino-9-benzyl-2-(3-ethoxypropoxy)purine (354 mg, 1.08 mmol) andbromine (1.0 ml) were dissolved in methylene chloride (50 ml). Thesolution was stirred at room temperature for 2 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and the solvent was removed. Theresidue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (289 mg, yield 66%).

¹H-NMR(DMSO-d₆) δ: 7.37(2H, br s), 7.36-7.23(5H, m), 5.26(2H, s),4.26(2H, t, J=6.4 Hz), 3.47(2H, t, J=6.4 Hz), 3.40(2H, q, J=7.0 Hz),1.90(2H, m), 1.09(3H, t, J=7.0 Hz).

Reference Example 1096-Amino-9-benzyl-2-(3-ethoxypropoxy)-8-methoxypurine

To 6-amino-9-benzyl-8-bromo-2-(3-ethoxypropoxy)purine (250 mg, 0.36mmol) in 20 ml of methanol was added 1N aqueous sodium hydroxide (80ml). The mixture was refluxed on heating under stirring for 2 hours. Thereaction mixture was concentrated in vacuo to dryness. To the residuewas added water and the mixture was extracted with chloroform. Theorganic layer was dried on sodium sulfate and the solvent was removed.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (187 mg, yield 85%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.23(5H, m), 6.88(2H, br s), 5.05(2H, s),4.23(2H, t, J=6.4 Hz), 4.05(3H, s), 3.47(2H, t, J=6.4 Hz), 3.38(2H, q,J=7.0 Hz), 1.89(2H, m), 1.10(3H, t, J=7.0 Hz).

Reference Example 110 6-Amino-9-benzyl-2-(4-hydroxybutoxy)purine

Sodium (150 mg, 6.5 mmol) in 5 ml of 1,5-butanediol were added6-amino-9-benzyl-2-chloropurine (500 mg, 1.93 mmol) and DMF (10 ml). Themixture was heated at 120° C. for 1 hour. The reaction mixture wasconcentrated in vacuo to dryness. To the residue was added water and themixture was extracted with chloroform. The organic layer was dried onsodium sulfate and the solvent was removed. The residue was purifiedwith silica gel chromatography (3% methanol/chloroform) to give thesubject compound (336 mg, yield 56%).

¹H-NMR(DMSO-d₆) δ: 8.04(1H, s), 7.37-7.25(5H, m), 7.22(2H, br s),5.26(2H, s), 4.46(1H, t, J=5.3 Hz), 4.22(2H, t, J=6.6 Hz), 3.43(2H, m),1.71(2H, m), 1.53(2H, m).

Reference Example 111 6-Amino-9-benzyl-8-bromo-2-(4-hydroxybutoxy)purine

6-Amino-9-benzyl-2-(4-hydroxybutoxy)purine (200 mg, 0.638 mmol) andbromine (1.0 ml) were dissolved in methylene chloride (50 ml). Thesolution was stirred at room temperature for 2 hours. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and the solvent was removed. Theresidue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (213 mg, yield 85%).

¹H-NMR(DMSO-d₆) δ: 7.44(2H, br s), 7.39-7.24(5H, m), 5.26(2H, s),4.45(1H, t, J=5.1 Hz)₁ 4.23(2H, t, J=6.6 Hz), 3.44(2H, m), 1.71(2H, m),1.54(2H, m).

Reference Example 1126-Amino-9-benzyl-2-(4-hydroxybutoxy)-8-methoxypurine

To 6-amino-9-benzyl-8-bromo-2-(4-hydroxybutoxy)purine (185 mg, 0.472mmol) in 10 ml of methanol was added 1N aqueous sodium hydroxide (40ml). The mixture was refluxed on heating under stirring for 2 hours. Thereaction mixture was concentrated in vacuo to dryness. To the residuewas added water and the mixture was extracted with chloroform. Theorganic layer was dried on sodium sulfate and the solvent was removed.The residue was purified with silica gel chromatography (2%methanol/chloroform) to give the subject compound (123 mg, yield 68%).

¹H-NMR(DMSO-d₆) δ: 7.37-7.23(5H, m), 6.87(2H, br s), 5.04(2H, s),4.43(1H, br s), 4.18(2H, t, J=6.4 Hz), 3.43(2H, t, J=6.6 Hz), 1.68(2H,m), 1.53(2H, m).

Reference Example 113 6-Amino-9-benzyl-2-(2-methoxyethoxy)purine

Sodium (66 mg, 2.9 mmol) in 50 ml of 2-methoxyethanol was added6-amino-9-benzyl-2-chloropurine (150 mg, 0.58 mmol) and DMF (10 ml). Themixture was heated at 130° C. for 6 hour. The reaction mixture wasconcentrated in vacuo to dryness. To the residue was added water and themixture was extracted with chloroform. The organic layer was dried onsodium sulfate and concentrated in vacuo to dryness. The residue waspurified with silica gel chromatography (3% methanol/chloroform) to givethe subject compound (123 mg, yield 71%).

¹H-NMR(DMSO-d₆) δ: 8.05(1H, s), 7.36-7.27(5H, m), 7.23(2H, br s),5.26(2H, s), 4.32(2H, t, J=4.6 Hz), 3.61(2H, t, J=4.6 Hz), 3.28(3H, s).

Reference Example 114 6-Amino-9-benzyl-8-bromo-2-(2-methoxyethoxy)purine

6-Amino-9-benzyl-2-(2-methoxyethoxy)purine (93 mg, 0.31 mmol) andbromine (1 ml) were dissolved in methylene chloride (100 ml). Thesolution was stirred at room temperature for 1 hour. Aqueous sodiumthiosulfate was added to the reaction mixture. The organic layer wasseparated, dried on sodium sulfate and concentrated in vacuo to dryness.The residue was purified with silica gel chromatography (1%methanol/chloroform) to give the subject compound (75 mg, yield 64%).

¹H-NMR(DMSO-d₆) δ: 7.46(2H, br s), 7.38-7.23(5H, m), 5.25(2H, s),4.33(2H, t, J=4.6 Hz), 3.61(2H, t, J=4.6 Hz), 3.28(3H, s).

Reference Example 1156-Amino-9-benzyl-8-methoxy-2-(2-methoxyethoxy)purine

6-Amino-9-benzyl-8-bromo-2-(2-methoxyethoxy)purine (69 mg, 0.18 mmol) inmethanol (50 ml) was dissolved in 28% sodium methoxide/methanol (1 ml)and the mixture was refluxed on heating under stirring for 5 hours. Thereaction mixture was concentrated in vacuo to dryness, and to theresidue was added water. The solution was extracted with chloroform andthe organic layer was dried on sodium sulfate and concentrated in vacuoto dryness. The residue was purified with silica gel chromatography (3%methanol/chloroform) to give the subject compound (26 mg, yield 43%).

¹H-NMR(DMSO-d₆) δ: 7.36-7.23(5H, m), 6.88(2H, br s), 5.04(2H, s),4.29(2H, t, J=4.6 Hz), 4.04(3H, s), 3.60(2H, t, J=4.6 Hz), 3.28(3H, s).

INDUSTRIAL APPLICABILITY

According to the present invention an interferon inducer containing acompound of the present invention as an active agent is provided. Theinterferon inducer of the present invention has inducing and activatingactivity for biosynthesis of interferon and therefore, is useful astherapeutic agents based on biological activities of interferon, such asantiviral activity, preventing activity of cell growth, immunemodulation etc., that is, therapeutic agents for virus infected diseases(e.g. hepatitis C, hepatitis B), anticancer agents and agents forimmunologic diseases.

What is claimed is:
 1. A heterocyclic compound of the following formula(I):

wherein X is sulfur atom, oxygen atom or —NR^(3a)— (in which R^(3a) ishydrogen atom, C₁₋₁₀ alkyl group, C₃₋₇ cycloalkyl group, or C₁₋₁₀ alkylsubstituted by C₃₋₆ cyclo-alkyl group, hydroxy group, C₃₋₆ alkoxy group,amino group, cyano group, aryl group, aryl group substituted by C₁₋₆alkoxy, hydroxy or halogen, halogen atom, or nitro group, or may form aheterocyclic ring or a substituted heterocyclic ring together with R¹via the nitrogen atom, wherein said substituent means C₁₋₆ alkyl group,hydroxy C₁₋₆ alkyl group, C₁₋₆ alkoxy C₁₋₆ alkyl group, hydroxy group,C₁₋₆ alkoxy group, or cyano group), R¹ is C₁₋₁₀ alkyl group; C₃₋₇cycloalkyl group; C₃₋₇ cycloalkyl substituted by C₁₋₆ alkyl; a groupselected from C₁₋₁₀ alkyl group, C₃₋₇ cycloalkyl group or C₁₋₆alkyl-substituted C₃₋₇ cycloalkyl group, which is substituted by C₃₋₆cycloalkyl group, hydroxy group, C₁₋₆ alkoxy group, C₁₋₆ alkoxy groupsubstituted by C₁₋₆ alkoxy, hydroxy or halogen, amino group, C₁₋₆alkylamino group, cyano group, nitro group, acyl group, carboxyl group,C₂₋₇ alkoxycarbonyl group, halogen atom, mercapto group, C₁₋₆ alkylthiogroup, C₁₋₆ alkylthio group substituted by C₁₋₆ alkoxy, C₁₋₆ alkylthio,hydroxy or halogen, aryl group, aryl group substituted by C₁₋₆ alkoxy,hydroxy or halogen, or heterocyclic group; aryl group; aryl groupsubstituted by C₁₋₆ alkyl group, hydroxy C₁₋₆ alkyl group, C₁₋₆ alkoxyC₁₋₆ alkyl group, hydroxy group, C₁₋₆ alkoxy group, cyano group, aminogroup, C₁₋₆ alkylamino group, C₂₋₇ alkoxycarbonyl group, acyl group,nitro group, halogen atom, aryl group, aryl group substituted by C₁₋₆alkoxy, hydroxy or halogen, or heterocyclic group; heterocyclic group;or heterocyclic group substituted by C₁₋₆ alkyl group, hydroxy C₁₋₆alkyl group, C₁₋₆ alkoxy C₁₋₆ alkyl group, hydroxy group, C₁₋₆ alkoxygroup, cyano group, nitro group, halogen atom, amino group, C₁₋₆alkylamino group, C₂₋₇ alkoxycarbonyl group, acyl group, aryl group,aryl group substituted by C₁₋₆ alkoxy, hydroxy or halogen orheterocyclic group, and R² is hydrogen atom, or one or more substituentson the benzene ring, and said substituent is the same or different andis hydroxy group, C₁₋₆ alkyl group, C₁₋₆ alkyl group substituted byhydroxy group, C₁₋₆ alkoxy group, carboxyl, C₂₋₇ alkoxycarbonyl group orhalogen atom, C₁₋₆ alkoxy group, C₁₋₆ alkoxy group substituted byhydroxy group, C₁₋₆ alkoxy group, carboxyl, C₂₋₇ alkoxycarbonyl group orhalogen atom, C₁₋₆ alkanoyl group, C₁₋₆ alkanoyl group substituted byhydroxy group, C₁₋₆ alkoxy group, carboxyl, C₂₋₇ alkoxycarbonyl group orhalogen atom, aroyl group, aroyl group substituted by hydroxy group,C₁₋₆ alkoxy group, carboxyl, C₂₋₇ alkoxycarbonyl group or halogen atom,carboxyl group, C₂₋₇ alkoxycarbonyl group, C₂₋₇ alkoxycarbonyl groupsubstituted by hydroxy group, C₁₋₆ alkoxy group, carboxyl, C₂₋₇alkoxycarbonyl group or halogen atom, amino group, C₁₋₆ alkylaminogroup, di(C₁₋₆ alkyl)amino group, carbamoyl group, C₁₋₆ alkylcarbamoylgroup, di(C₁₋₆ alkyl)carbamoyl group, halogen atom, nitro group, orcyano group, or a pharmaceutically acceptable salt thereof.
 2. Theheterocyclic compound of claim 1, wherein X is sulfur atom, or itspharmaceutically acceptable salt.
 3. The heterocyclic compound of claim1, wherein X is oxygen atom, or its pharmaceutically acceptable salt. 4.The heterocyclic compound of claim 1, wherein X is —NH—, or itspharmaceutically acceptable salt.
 5. The heterocyclic compound of claim1, wherein X is —NR^(3a)— in which R^(3a) means C₁₋₆ alkyl group orsubstituted C₁₋₆ alkyl substituted by C₃₋₆ cycloalkyl group, hydroxygroup, C₁₋₆ alkoxy group, amino group, cyano group, aryl group, arylgroup substituted by C₁₋₆ alkoxy, hydroxy or halogen, halogen atom, ornitro group, or its pharmaceutically acceptable salt.
 6. Theheterocyclic compound of claim 1, wherein R^(3a) forms a heterocyclicring or a substituted heterocyclic ring together with R¹ via thenitrogen atom, or its pharmaceutically acceptable salt.
 7. Theheterocyclic compound of claim 1, wherein R¹ means C₁₋₆ alkyl group orsubstituted C₁₋₆ alkoxy, C₁₋₆ alkylthio, C₂₋₇ alkoxycarbonyl, hydroxy,halogen atom, cyano, amino, cyclohexyl, trifluoromethyl, pyridyl,phenyl, methoxyphenyl, hydroxyphenyl, halophenyl or thienyl, or itspharmaceutically acceptable salt.
 8. The heterocyclic compound of claim1, wherein R¹ means C₁₋₆ substituted alkyl group and said substituent ishydroxyl, or its pharmaceutically acceptable salt. 9.6-Amino-9-benzyl-8-hydroxy-2-[(2-hydroxyethyl)thio]purine or itspharmaceutically acceptable salt. 10.6-Amino-9-(4-fluorobenzyl)-8-hydroxy-2-(2-methoxyethoxy)purine or itspharmaceutically acceptable salt. 11.6-Amino-9-benzyl-8-hydroxy-2-(2-methoxyethoxy)purine or itspharmaceutically acceptable salt.
 12. A pharmaceutical compositioncomprising a heterocyclic compound or its pharmaceutically acceptablesalt of claim 1, as an active ingredient.
 13. A method for inducinginterferons in a patient having virus infected disease, cancer orallergic disease by administering the heterocyclic compound of claim 1,or its pharmaceutically acceptable salt to the patient in an amounteffective to induce interferons.